Моделювання фотодіодної структури на основі гетеропереходу ZnO/Si
In this work, a self-powered photodetector based on a bulk ZnO/Si p–n heterojunction is numerically investigated and analyzed using the Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D). The energy band diagram, electron-hole generation and recombination rates, current-voltage (J–V) chara...
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Technology and design in electronic equipment| _version_ | 1872552535423713280 |
|---|---|
| author | Virt, Ihor Padalka, Ivan |
| author_facet | Virt, Ihor Padalka, Ivan |
| author_institution_txt_mv | [
{
"author": "Ihor Virt",
"institution": "Ivan Franko State Pedagogical University of Drogobych, Ukraine"
},
{
"author": "Ivan Padalka",
"institution": "Ivan Franko State Pedagogical University of Drogobych, Ukraine"
}
] |
| author_sort | Virt, Ihor |
| baseUrl_str | https://www.tkea.com.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2026-08-03T14:14:28Z |
| description | In this work, a self-powered photodetector based on a bulk ZnO/Si p–n heterojunction is numerically investigated and analyzed using the Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D). The energy band diagram, electron-hole generation and recombination rates, current-voltage (J–V) characteristics, spectral photosensitivity response, and specific detectivity are examined. To optimize photodetector performance, the effects of absorber layer thickness, shallow acceptor and donor densities, and defect density were systematically studied. Various electron transport parameters of ZnO were also considered. The responsivity and specific detectivity of the simulated photodetector are 0.23 A/W and 1.1·1010 Jones, respectively. |
| doi_str_mv | 10.15222/TKEA2026.1.17 |
| first_indexed | 2026-08-04T01:00:59Z |
| format | Article |
| fulltext |
Teсhnology and design in electronic equipment, 2026, N 1 17ISSN 3083-6530 (Print)
ISSN 3083-6549 (Online)
17
SENSORS
УДК 621.382.592
MODELING OF A PHOTODIODE STRUCTURE BASED
ON A HETEROJUNCTION ZnO/Si
Current trends in sensor instrumentation encompass
a range of promising emerging technologies alongside
innovative chemical and physical processes, as well as
advanced systems for signal generation, conversion, and
transmission. Photodetectors, which directly convert
light into electrical signals, have been developed for
numerous applications, including medical diagnostics,
aviation, target recognition, and related fields [1]. Self-
powered photodetectors based on p–n junctions exhibit
outstanding photovoltaic characteristics—such as fast
response speed, wide linear dynamic range, and low
noise—and have demonstrated significant progress in
recent years [2]. To further enhance these parameters,
research groups are developing dedicated simulation
tools and conducting photovoltaic device modeling
studies. Simulation methods provide valuable insight
into the physical phenomena governing photovoltaic
cell operation. For this purpose, SCAPS-1D (Solar Cell
Capacitance Simulator—One Dimensional) software has
been widely adopted [3].
The built-in electric field present at the heterojunction
interface between dissimilar materials acts as a driving
force for the efficient separation of photogenerated charge
carriers, thereby sustaining a continuous photocurrent.
When electron-hole pairs are generated within the
depletion region of a p–n junction, the local electric field
separates them, allowing the carriers to be collected at
the respective external contacts.
Currently, theoretical studies of silicon-based hetero-
structures are widely conducted using SCAPS software.
In particular, planar configurations of metal oxides and
silicon, such as ZnO/Si, are commonly employed as model
systems. Numerical analysis is performed to determine
the optimal conditions for such photodetectors, and the
In this work, a self-powered photodetector based on a bulk ZnO/Si p–n heterojunction is numerically investigated and analyzed
using the Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D). The energy band diagram, electron-hole generation
and recombination rates, current-voltage (J–V) characteristics, spectral photosensitivity response, and specific detectivity
are examined. To optimize photodetector performance, the effects of absorber layer thickness, shallow acceptor and donor
densities, and defect density were systematically studied. Various electron transport parameters of ZnO were also considered.
The responsivity and specific detectivity of the simulated photodetector are 0.23 A/W and 1.1·1010 Jones, respectively.
Keywords: photovoltaic cell, photodetector, numerical simulation, electron transport material (ETM), ZnO, heterostructure,
SCAPS-1D program.
factors governing their performance are systematically
investigated. Numerical modeling represents a critically
important stage in optimizing device architectures prior
to experimental fabrication and testing. Furthermore,
simulation results demonstrate that well-aligned energy
bands in the metal oxide and silicon lead to improved
device performance, whereas misalignment of the bands
results in increased charge recombination rates and
reduced efficiency. The ability of a device to reliably
detect radiation is a fundamental requirement for its
practical industrial application.
Thin-film metal oxides (TFMOs) continue to attract
considerable interest due to their versatility in sensing
applications. Interest in modeling TFMOs has grown
substantially over recent decades, driven by their
relative simplicity and compatibility with available
simulation tools. Nevertheless, most TFMO-based
devices still exhibit low conversion efficiencies, and
laboratory efforts to achieve optimal energy conversion
continue despite advances in numerous physical and
chemical fabrication methods for photovoltaic cells. This
limitation can be attributed to several loss mechanisms
inherent in absorber layer structures. Zinc oxide is
widely used in optoelectronics owing to its excellent
optical and electronic properties, and has established
itself as a multifunctional material over the past five
decades. ZnO is a wide-bandgap semiconductor with
a bandgap of 3.36 – 3.41 eV, and is also regarded as
an effective anti-reflection material suitable for optical
detection and a broad range of optoelectronic applications
[4]. Among heterojunction device architectures, the
ZnO/Si thin-film heterostructure is one of the most
extensively optimized configurations, demonstrating
high photodetection efficiency. Key device parameters—
DOI: 10.15222/TKEA2026.1.17
Ihor VIRT, Ivan PADALKA
Ukraine, Ivan Franko State Pedagogical University of Drohobych
Teсhnology and design in electronic equipment, 2026, N 118 ISSN 3083-6530 (Print)
ISSN 3083-6549 (Online)
18
SENSORS
including absorber and electron transport layer (ETL)
thickness, series resistance, shunt resistance, and
operating temperature—can be evaluated together with
corresponding characteristics such as carrier generation
and recombination rates, capacitance–voltage (C–V)
profiles, current density–voltage (J–V) curves, and
quantum efficiency. These performance metrics are
strongly influenced by crystallographic quality, surface
morphology, and film density, making the choice of ZnO
deposition technique critical for fabricating high-quality
photosensitive structures [5]. Numerical simulations of
low-cost ZnO/Si devices have previously been carried out
using various tools, including AFORS-HET and PC1D
[6], [7]. ZnO/Si photocells have also been modeled with
Silvaco ATLAS, where bandgap profiles and electric field
distributions at the Si/ZnO interface were examined [8].
The SCAPS-1D software enables numerical investigation
of hetero- and multi-junction photovoltaic devices,
supporting the extraction of photovoltaic parameters
as well as non-standard measurements, including C–V,
G–V (conductance–voltage), and C–f (capacitance–
frequency) characteristics. It has also been applied to
simulate ZnO/Si solar cells with interface defects [9].
Simulations were carried out using an iterative approach,
solving the Poisson equation together with the continuity
equations for electrons and holes [10], with photodetector
parameters extracted under different spectral conditions.
The resulting SCAPS-1D outputs can be benchmarked
against those obtained from other simulation platforms
[11], [12]. Among the most widely used simulation tools
in recent years are COMSOL, Silvaco ATLAS, AMPS,
wxAMPS, and SCAPS [13], [14].
Among the available simulation tools, SCAPS-1D
is regarded as particularly accessible, offering a broad
range of input and output parameters [15], [16].
Compared to other common platforms for photodetector
analysis—such as TCAD, ANSYS Lumerical Charge,
and COMSOL Multiphysics—SCAPS-1D occupies a
distinct and well-established position in the field. Its
open-source nature and intuitive interface have made it a
de facto standard in photovoltaic research. The reliability
of the software is supported by a strong agreement
between simulation results and experimental data for
both p–n and n–i–p device structures. SCAPS-1D is a
numerical platform for analyzing and optimizing thin-
film photovoltaic homo- and heterojunction structures
through the self-consistent solution of Poisson’s equation
and the carrier continuity equations, enabling detailed
analysis of multilayer heterojunctions by allowing
independent variation of layer thickness, doping
concentration, defect density, and bandgap [17], [18].
The simulator is built upon the numerical solution of
the fundamental semiconductor equations—namely, the
Poisson equation and the carrier continuity equations—
ensuring accurate computation of J–V characteristics
and quantum efficiency [19], [20]. This physically
rigorous approach yields high fidelity in modeling the
optoelectronic processes occurring within photodetector
structures. The strong correspondence between simulated
and experimental results establishes SCAPS-1D as a
dependable tool for predictive device design, enabling
the effective development of sensors for optical imaging,
environmental monitoring, and operation across a broad
spectral range.
The aim of this work is to investigate and analyze,
by means of numerical simulation within the SCAPS-1D
software environment, the parameters and characteristics
of a ZnO/Si heterojunction photodetector. Particular
attention is given to the influence of ZnO oxide layers
grown on silicon substrates by pulsed laser deposition
[21], [22] on the responsivity and specific detectivity of
the device in the ultraviolet spectral region (300 nm).
Research Methodology and Subject
of Investigation
This work employs a planar p–n heterojunction
structure consisting of a p-type Si layer and an n-type
ZnO thin film. Default device parameters are applied
across configurations with different active layers.
The photoelectric performance of the n–p ZnO/Si
heterojunction was numerically evaluated using
the fundamental equations governing electron–hole
junctions, with simulations carried out in SCAPS-1D.
Based on input parameters such as layer bandgap,
thickness, and doping concentration, the software
predicts key photovoltaic characteristics—including
current–voltage curves, quantum efficiency, and energy
band diagrams. The principal input parameters include
dielectric permittivity, bandgap energy (Eg), electron
affinity, carrier mobility, and doping concentrations
(ND, NA). The generation rate is computed from the
optical absorption profile under a specified illumination
spectrum, while the recombination rate is determined
self-consistently alongside the carrier transport equations.
The platform also supports parametric optimization—
for example, systematic variation of layer thickness or
doping concentration—enabling quantitative assessment
of their impact on power conversion efficiency (PCE)
and fill factor (FF).
The thickness of the metal oxide film was varied in
the range of 50 – 700 nm for the absorber layer, while the
base layer (industrial-grade silicon wafers) had a fixed
thickness of 250 µm. Planar configurations offer the
advantage of low-temperature processing, which enables
the fabrication of flexible devices without inducing
substrate degradation. Furthermore, such configurations
are compatible with tandem junction architectures
incorporating a variety of semiconductor materials. The
simulation results identify the optimal photodetection
efficiency for a range of p–n parameter values of the
ZnO/Si heterojunction.
Teсhnology and design in electronic equipment, 2026, N 1 19ISSN 3083-6530 (Print)
ISSN 3083-6549 (Online)
19
SENSORS
Since Si is a p-type semiconductor, an n-type
electronically conductive metal oxide was incorporated
as the photoabsorber within the heterojunction structure.
ZnO thin film, owing to its favorable optoelectronic
properties, serves as an n-type material functioning
simultaneously as both the window and active layer. The
relatively thick Si base provides strong optical absorption
and forms a heterojunction that is well-matched to n-type
thin-film overlayers. This configuration enables enhanced
photocurrent generation upon interaction of ultraviolet
photons with the active layer, allowing absorption of all
photons with energies exceeding the bandgap of ZnO.
Together, the n-type absorption layer and the p-type
silicon layer constitute a conventional photovoltaic
structure with a window–absorber n–p junction, as
illustrated in Fig. 1. In a homojunction device, both
regions are composed of the same semiconductor
material, whereas in a heterojunction device they consist
of two distinct materials.
The interface between the p- and n-type regions
is regarded as the most critical component of any
photovoltaic device. Within this region of the hetero-
structure, energetic photons absorbed in the space-charge
depletion region drive the separation of electron-hole
pairs, a process that plays a decisive role in determining
overall device performance.
Numerical Simulation Using SCAPS-1D
Simulations were performed using SCAPS version
3.3.12, a software package widely adopted for modeling
photovoltaic cells based on polycrystalline thin films,
which also supports the simulation of step junctions. The
principal photovoltaic parameters—open-circuit voltage
(VOC), short-circuit current density (JSC), fill factor (FF),
quantum efficiency (QE), and the band structure of the
heterojunction—are key determinants of photodetector
responsivity [23], [24]. Simulations were conducted
under spectral illumination conditions, within which a
variety of homo- and heterojunction architectures can
be proposed and evaluated [25], [26].
The simulation framework is based on the self-
consistent numerical solution of Poisson’s equation and
the semiconductor continuity equations. The continuity
equations, solved within the junction interface region,
govern charge carrier transport inside the device—
accounting for electrostatic potential distribution, carrier
drift and diffusion, and electron-hole recombination
processes [27]. Poisson’s equation is given as
2φ ( )
ε D A
q n p N N =- - + - , (1)
where φ is the electrostatic potential;
ε is the dielectric permittivity;
q is the elementary charge;
NA, ND are the acceptor and donor densities, respectively;
p, n are the hole and electron concentrations, respectively.
The semiconductor carrier transport equations are
given as
( )pJ q G R = - ; (2)
( )nJ q R G = - , (3)
where Jp, Jn are the hole and electron current density, res-
pectively;
G is denotes the optical generation rate;
R is the total recombination, including direct and
indirect recombination.
All these parameters are a function of the interface
coordinate (coordinate position x). Introducing the
effective potentials Vn and Vp as characteristic quantities
of the interface region, we obtain
Δγn
GV V
g
= + ; (4)
Δ(1 γ)p
GV V
g
= - - . (5)
The parameters ∆G and γ take into account changes in
the band structure, such as the density of states of the band
gap, and also take into account Fermi–Dirac statistics.
Then the hole and electron current densities appearing
in equations (2) and (3) are given by
μ μp p p pJ q p V kT p=- ⋅ - ⋅ ; (6)
μ μn n n nJ q n V kT n=- ⋅ - ⋅ , (7)
where μn, μp are the electron and hole mobilities,
respectively.
Fig. 1. Schematic representation of the n-ZnO/p-Si hetero-
structure (a) and device configuration used for numerical
modeling in the SCAPS-1D simulation environment (b)
b)
Left
contact
front
Right
contact
back
J V
Light
n-ZnO p-Si
a)
p-Si
n-ZnO
Ag
Ag
Teсhnology and design in electronic equipment, 2026, N 120 ISSN 3083-6530 (Print)
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SENSORS
The software interfaces use all the variables listed in
Table 1 and are the device input parameters during the
simulation.
All variables listed in Table 1 serve as device input
parameters during simulation and are directly accessible
through the software interface. The complete modeling
procedure for characterizing a heterojunction is outlined
in the flowchart presented in Fig. 2.
The key outputs generated by SCAPS-1D include:
• J–V curves, used for optimizing the power con ver-
sion efficiency;
• quantum efficiency describing photon-to-carrier
conversion as a function of wavelength;
• energy band diagrams providing visualization of
band alignment and Fermi-level (EF) distribution;
• capacitance–voltage characteristics, enabling
determination of carrier concentration and built-in
potential.
In each simulation run, the primary variable
(voltage V, frequency f, or current I) is swept across a
specified range. The resulting outputs include computed
parameters and characteristics—such as J–V and C–V
curves, C–f spectra, generation rate profiles Q(λ), energy
band diagrams, carrier concentration distributions, and
electron and hole current densities. All simulation results
are exported in ASCII format and presented graphically
for analysis and interpretation.
Results and Discussion
SCAPS-1D Simulation of the n–p ZnO/Si Heterojunction
This study examined the effect of ZnO layer thickness
on the characteristics of the ZnO/Si heterojunction. The
simulation incorporated a nickel-doped zinc oxide layer
serving as an ultraviolet-absorbing medium. J–V curves
were extracted from spectral measurements performed
both in the dark and under illumination, reflecting realistic
device operating conditions. The highest fill factor of
63.18% and power conversion efficiency of 7.71% were
achieved for the nanostructured ZnO/Si heterojunction
with an absorber layer thickness of 100 nm.
Table 1
Device parameters: ZnO layer and substrate p-Si [28]
Parameters n-ZnO p-Si
Relative permittivity, εr 9 11.9
Energy gap, Eg (eV) 3.3 1.12
Thickness, d (μm) variable 250
Electronic affinity, χ (eV) 4.35 4.05
Effective density of states in the
conduction band, NC (cm−3) 4.4·1018 2.8·1019
Effective density of states in the
valence band, NV (cm−3) 7.1·1019 1.04·1018
Donor concentration, ND (cm−3) variable —
Acceptor сoncentration, NA (cm−3) — 7.0·1015
Electron mobility, μn (cm2/V·s) 100 1500
Hole mobility, μp (cm2/V·s) 25 480
Electron thermal velocity, Vth.e
(cm/s) 107 107
Hole thermal velocity, Vth.h (cm/s) 107 107
Temperature, T (K) 300 300
Fig. 2. SCAPS-1D simulation platform for modeling the optoelectronic properties of the n-ZnO/p-Si heterojunction
1. Define problem.
2. Working point.
3. Select calculations.
4. Start calculations.
5. Analyze results.
Teсhnology and design in electronic equipment, 2026, N 1 21ISSN 3083-6530 (Print)
ISSN 3083-6549 (Online)
21
SENSORS
The input parameters used in the SCAPS-1D
simulations were adopted from the literature and
are based on the material properties of ZnO and Si
summarized in Table 1.
The input parameters for the front and rear contacts
were additionally optimized using SCAPS-1D.
Properties of the ZnO Absorber Layer
The absorption layer consists of an n-type zinc
oxide semiconductor. ZnO exhibits an electron affinity
of 4.5 eV and favorable carrier mobility characteristics.
In addition, ZnO possesses distinctive optoelectronic
properties, high mechanical strength, and a large
refractive index, making it a highly suitable material for a
broad range of applications, including photovoltaics. The
density of states is governed by the strong hybridization
between the constituent atomic orbitals. Among all
orbital contributions, the O2p orbital electrons exert the
dominant influence on the position of the Fermi level
EF. The electronic band structure and density of states
represent energy spectra that describe the dependence
of energy eigenvalues on wave vectors in the reciprocal
(k-space) of a crystal lattice, encoding information about
both intramolecular bond interactions and intermolecular
forces.
The electron affinity of ZnO, acting as the electron
transport material, ranges from 3.60 to 4.60 eV. By
adjusting this parameter, the band offset at the interface
with the absorber layer can be tuned, effectively shifting
the energy band alignment. A schematic of the energy
band diagram of the simulated n-ZnO/p-Si photovoltaic
structure is presented in Fig. 3. In this configuration, the
n-ZnO layer serves as the photoabsorber, while the p-Si
layer functions as the primary charge transport medium.
Simulated Current-Voltage Characteristics
of the ZnO/Si Heterojunction
Representative transport curves across the hetero-
junction interface. Representative transport curves
across the ZnO/Si heterojunction interface were
obtained under the following simulation conditions:
illumination incident from the left contact, voltage
bias applied at the right contact, and the left contact
held at ground potential. Layer interfaces were defined
accordingly. The simulation first computed the energy
band structure, followed by extraction of the J–V and
C–V characteristics. The simulated ZnO/Si thin-film
heterojunction yielded a fill factor of FF ≈ 63.18% and
a power conversion efficiency of η ≈ 7.71%. Fig. 4
presents the dark and illuminated current–voltage
characteristics over a bias range of − 0.8 V to + 0.8 V,
where the photocurrent consistently exceeded the dark
current [29]. The photovoltaic parameters derived from
the J–V curves are summarized in Table 2.
Careful analysis reveals the coexistence of several
conduction mechanisms, giving rise to non-ideal diode
Fig. 3. Spatial distribution of energy bands (a) and electrostatic
potential in ZnO/Si heterostructures (b)
a)
(1.01)
0
–1.0
–2.0
(–3.06)
Еn
er
gy
, e
V
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1
Distance, μm
b)
1.0
0.8
0.6
0.4
0.2
0
El
ec
tr
os
ta
tic
p
ot
en
tia
l,
un
its
k
T/
q
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1
Distance, μm
Fig. 4. Current–voltage characteristics of the ZnO/Si photo-
detector, presented on a linear scale (a) and a semi-logarithmic
scale (b):
1 — dark; 2 — under UV illumination at λ = 300 nm
a)
40
30
20
10
0
–10
(–17)
C
ur
re
nt
d
en
si
ty
, m
A
/c
m
2
– 0.6 –0.4 – 0.2 0 0.2 0.4 0.6 0.8
Voltage, V
1
2
b)
(40)
10
1
0,1
(0,04)
C
ur
re
nt
d
en
si
ty
, m
A
/c
m
2
0.50 0.55 0.60 0.65 0.70 0.75 0.80
Voltage, V
1 2
EV EF
EC
EN
Teсhnology and design in electronic equipment, 2026, N 122 ISSN 3083-6530 (Print)
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SENSORS
behavior in distinct operating regions. The forward bias
regime can be decomposed into three characteristic
transport regimes: generation-recombination current,
diffusion current, and an ohmic regime governed by series
resistance [30]. At low forward bias, carrier transport is
dominated by recombination via the Shockley–Read–
Hall (SRH) mechanism, involving defect states and trap
centers within the depletion region. At moderate forward
bias, diffusion current becomes the primary transport
mechanism, as injected minority carriers—holes in the
n-type region and electrons in the p-type region—diffuse
into the quasi-neutral regions, producing an exponential
current–voltage dependence. In this regime, the J–V
characteristic approaches ideal Shockley behavior with
an ideality factor close to unity, indicative of transport
limited by minority carrier concentration gradients.
The built-in potential of the heterojunction facilitates
the separation of photogenerated charge carriers. In
the absence of an external bias, the resulting potential
difference across the device constitutes the fundamental
driving mechanism of the photovoltaic effect. The short-
circuit current exhibits a linear dependence on incident
optical power, while the open-circuit voltage scales
logarithmically with decreasing power, consistent with
the heterojunction equation under illumination.
The dark J–V characteristic displays a nonlinear
increase in current with applied voltage, which becomes
particularly pronounced at higher bias levels. Under
illumination at a power density of 82.7 mW/cm2, the J–V
characteristic is recorded for both reverse and forward bias
conditions, as shown in Fig. 4. The carrier concentration
directly influences the shape of the J–V curves: as the
doping concentration increases, the resistivity decreases
and the current increases correspondingly.
The described device operates in a one-sided structure,
but ZnO plays an active role as the main absorbing layer
in the ultraviolet region. The internal electric field of the
heterojunction enables rapid separation of photoexcited
electrons and holes [31]. This behavior is attributed to
the high quality of the films and the low defect density
of the fabricated ZnO and Si nanostructures, consistent
with the estimated optical band gaps of the components
used [32].
The current measured at a given voltage under
illumination exceeds that recorded in the dark, confirming
that light absorption in the n-ZnO/p-Si heterojunction
generates a photocurrent through the formation of
electron–hole pairs (Fig. 5). The enhancement of the
reverse current under illumination is attributed to
the generation of additional charge carriers via light
absorption. The difference between the illuminated and
dark currents, Iill − Idark, is 13.9 mA. The properties of both
front and rear contacts can be independently adjusted, and
the interface defect density between adjacent layers can
be specified as a simulation input. Table 3 summarizes
the key simulated photovoltaic parameters—open-circuit
voltage VOC, short-circuit current density JSC, fill factor
FF, and power conversion efficiency η—extracted
under illumination. From the J–V curve of the ZnO/Si
Table 2
Summary of input parameters for the back and front contacts
employed in SCAPS-1D simulations of metal oxide-based
heterojunction devices
Parameter Back
contact
Front
contact
Thermionic emission/surface
recombination velocity Holes
(cm/s)
1.00‧107 1.00‧107
Thermionic emission/surface
recombination velocity Electrons
(cm/s)
1.00‧107 1.00‧107
Metal work function (eV) 5.021 —
Main carrier barrier height (eV)
relative to Ef
0.221 0.4
Main carrier barrier height (eV)
relative to Ev
0 0.227
b)
(0.01)
–2.5
–5.0
–7.5
–10.0
(–14) C
ur
re
nt
d
en
si
ty
, m
A
/c
m
2
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1
Distance, μm
1
2
Fig. 5. Modeled carrier concentration (a) and current density (b)
distributions of the ZnO/Si photodetector under
UV illumination:
1 — electrons; 2 — holes; 3 — total concentration
Table 3
Simulated photoelectric parameters of the n-ZnO/p-Si
photovoltaic heterojunction
VOC, V JSC, mА/сm2 FF, % η, %
0.725 13.9 63.18 7.71
a)
1016
1014
1012
1010
(2·107) C
on
ce
nt
ra
tio
n,
c
m
–3
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1
Distance, μm
1
2
3
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heterojunction photodetector, the short circuit current
JSC = 13.9 mA and the open circuit voltage VOC = 0.725 V
are obtained, consistent with the standard J–V response of
a photovoltaic cell under illumination [33]. Variation of
the electron affinity parameter affects the band alignment
at the heterojunction interface and, if not correctly
selected, results in a concurrent degradation of FF, JSC,
VOC, and η.
Effect of ZnO layer thickness on structured
heterojunction photovoltaic cells. In a typical n–p
heterojunction, incident radiation passes through the
absorber layer and partially through the conductive
substrate. Incident photons are absorbed by the n-type
semiconductor absorber layer, while unabsorbed photons
are dissipated as heat. The absorber layer consists of a
ZnO thin film, and the influence of doping concentration
on device efficiency and J–V characteristics has been
examined [34], [35]. Previous studies have demonstrated
that ZnO is the most suitable n-type material for high-
efficiency ZnO-based p–n heterojunction photovoltaic
cells [36]. In the present study, the absorber layer
thickness was varied in the range of 50 – 500 nm (Fig. 6).
These values fall within the optimized thickness range;
the absorber layer should be sufficiently thin to minimize
series resistance within the photovoltaic device. As
evident from the data shown in Fig. 6, the optimal
ZnO layer thickness lies in the range of 50 – 100 nm.
At this thickness, the heterostructure attains maximum
photosensitivity in the ultraviolet spectral region.
The optical absorption properties of each layer
can be defined either through a built-in analytical
model or by importing material property files from
the program’s internal library. Within the defect
configuration panel, recombination is categorized
into three distinct mechanisms: Auger recombination,
radiative recombination (both representing band-to-band
transitions) and SRH recombination, which proceeds
via mid-gap trap states. In the present model, only SRH
recombination is activated, defined by a single neutral
defect level with uniform energy distribution and a defect
density of 1·1015 см–3.
Therefore, the n-ZnO/p-Si heterostructure achieves
maximum photosensitivity in the ultraviolet spectral
region at an absorber layer thickness of approximately
50 – 100 nm.
Effect of absorber layer doping concentration on
device performance. The doping concentration of the
absorber layer has a significant influence on device
performance and was varied in the range of 1·1014 cm–3
to 1·1018 cm–3 to examine its effect on the simulated
characteristics.
A maximum power conversion efficiency of 7.71%
is achieved following the optimization and verification of
key simulation parameters. To further refine the properties
of each active layer, the effects of absorber thickness
and doping density on device performance (Fig. 7),
efficiency, and carrier recombination behavior were
systematically investigated. These results demonstrate that
SCAPS-1D is capable of detecting variations in
photovoltaic parameters and quantifying their impact
on simulation output.
The donor concentration in a semiconductor can be
controlled through intentional doping with extrinsic
impurities or by modifying intrinsic defect populations.
Zinc oxide, in particular, exhibits intrinsic n-type
conductivity. The primary intrinsic donor-type defects
in ZnO are oxygen vacancies and interstitial zinc
atoms. The donor concentration can also be tuned by
modifying the density of these intrinsic defects through
post-deposition treatments such as thermal annealing or
high-dose irradiation. As evident from Fig. 7, the optimal
donor concentration in the ZnO layer for achieving
high photocurrent responsivity lies in the range of
1014 – 1015 cm–3.
The influence of trap defect density Nt on the
heterostructure characteristics was also examined.
Using SRH recombination model [37], a defect level
was introduced with a mean energy of 0.58 eV within
the bandgap and a neutral Gaussian energy distribution.
Fig. 6. Current-voltage characteristics (a) and spectral respon-
sivity (b) of the n-ZnO/p-Si heterojunction at different ZnO
absorber layer thicknesses (nm):
1 — 50; 2 — 100; 3 — 200; 4 — 300; 5 — 500
(donor concentration in ZnO ND = 1015 cm–3)
a)
160
120
80
40
0
(–19)
C
ur
re
nt
d
en
si
ty
, m
A
/c
m
2
– 0.6 –0.4 –0.2 0 0.2 0.4 0.6 0.8
Voltage, V
125 4 3
b)
2.0
1.6
1.2
0.8
0.4
0Sp
ec
tra
l r
es
po
ns
iv
ity
, A
/W
300 310 320 330 340 350 360 370 380 390 400
Wavelength, nm
2
1
3
4
5
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24
SENSORS
The SRH recombination rate is defined by equation
2
τ ( ) τ ( )
i
p i n i
np nSRH
n n p n
-
=
+ + +
, (8)
where p, n denote the hole and electron concentrations;
τp, τn are the corresponding non equilibrium minority carrier
lifetimes;
ni is the intrinsic carrier concentration.
The model additionally computes the carrier diffusion
length, as SRH recombination is one of the most
prevalent recombination mechanisms in photodetector
structures [38]. In this study, the trap defect density
was set to Nt = 1·1015 cm–3, which proved optimal for
the given device configuration. The simulated device
characteristics exhibit a systematic degradation with
increasing defect density in the active absorber layer. The
simulation framework also allows the defect density of
the photoactive layer to be selectively disabled, enabling
assessment of its individual contribution to overall device
performance.
Graph of capacitance and conductivity of
a heterostructure. The capacitive characteristics of the
heterostructure—specifically the capacitance-voltage
(C–V) and capacitance-frequency (C–f) profiles—
were obtained by numerical simulation. The C–V
characteristics were evaluated over a bias range of ± 0.8 V
at a frequency of 1 MHz.
The dependence of the junction capacitance for an
abrupt heterojunction at zero bias is given in [39]:
2 1 2
1 2
ε ε 1
2(ε ε )
D A
D A bi
q N NC
N N V V
= ⋅
+ -
, (9)
where q is the elementary electron charge;
ε1, ND are the permittivity and donor carrier concentration of
the ZnO layer, respectively;
ε2, NA are the permittivity and acceptor carrier concentration
of the p-Si substrate, respectively.
The built-in potential Vbi is determined from the
difference in energy levels on the band diagram (see Fig. 3, a).
Its value at a donor concentration of ND = 1015 cm–3 in
the absorbing layer ZnO is Vbi = 2.8 V and varies only
slightly with changes in doping concentration. The values
of ND and NA estimated for the n-ZnO/p-Si heterojunction
are in good agreement with those used in the modeling.
Fig. 8 presents the simulated frequency dependence of
the electrical parameters of the n-ZnO/p-Si photovoltaic
cell under zero external bias. The frequency was swept
from 50 Hz to 5 MHz. Fig. 8, a shows that the capacitance
remains approximately constant with increasing frequency
throughout the simulated range. Two distinct regions are
identifiable in the C–f characteristics. At low frequencies,
the capacitance is nearly constant and approaches the
quasi-static (DC) limit. At high frequencies, a pronounced
variation is observed, attributed to trapped carriers
transitioning between occupied and unoccupied states
near the Fermi level. When the AC signal frequency
matches the characteristic time constant of these traps,
Fig. 7. Current-voltage characteristics (a) and spectral respon-
sivity (b) of the n-ZnO/p-Si heterojunction at different donor
concentrations in the ZnO layer (cm–3):
1 — 1014; 2 — 1015; 3 — 1016; 4 — 1017; 5 — 1018
(layer thickness 100 nm)
a)
0.01
0 C
ap
ac
ita
nc
e,
n
F/
cm
2
102 103 104 105 106
Frequency, Hz
b)
10–9
10–10
10–11
10–12 C
on
du
ct
an
ce
, S
/c
m
2
102 103 104 105 106
Frequency, Hz
Fig. 8. Frequency dependences of the barrier capacitance (a)
and specific admittance (b) of the n-ZnO/p-Si heterojunction
a) 40
30
20
10
0
– 10
(–18)
C
ur
re
nt
d
en
si
ty
, m
A
/c
m
2
(– 0,70) – 0.50 – 0.25 0 0.25 0.50 (0.80)
Voltage, V
1
2
4
3
5
b)
2.0
1.6
1.2
0.8
0.4
(0.1)Sp
ec
tra
l r
es
po
ns
iv
ity
, A
/W
300 310 320 330 340 350 360 370 380 390 400
Wavelength, nm
2
1
3 4
5
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SENSORS
peak losses associated with interface trap levels are
expected. For frequencies deviating slightly from this
resonance condition, the interface density of states and
the corresponding relaxation times can be estimated from
the C–f plots.
The interface state density at the heterojunction
interface was evaluated from the relationship between
the surface charge density Nss and the low-frequency
capacitance Css [40]:
ss
ss
CN
q A
=
⋅
, (10)
where A is the interface area.
The extracted interface state density is
Nss = 3.63·10–12 eV–1·cm–2.
In the MHz frequency range, significant changes
in capacitance are observed. At sufficiently high
frequencies, the device capacitance approaches the
geometric capacitance, resulting in an apparent increase
in the measured capacitance value when parasitic
inductance effects are neglected.
The frequency dependence of heterostructures
containing deep impurity levels arises from the charging
and discharging dynamics of deep-level traps within
the depletion region, which respond to the applied
measurement frequency. When deep energy levels
originate from a high concentration of intrinsic defects, the
Schibli – Milnes model can be employed to describe the
frequency dependence of the junction capacitance [41].
In the present work, this model was adopted to analyze
the C–f characteristics of the device. Furthermore, it was
confirmed that for short non equilibrium carrier lifetimes
τSRH (corresponding to the short-diode limit), the barrier
capacitance Cj is independent of the bulk layer thickness.
Fig. 8, b shows the simulated conductance-frequency
(G–f) characteristics of the ZnO/p-Si photovoltaic cell
at different frequencies. The conductance decreases to
values on the order of 10 – 12 S/cm2 at frequencies above
10 kHz. In the high-frequency region, the device response
is dominated by the series resistance and bulk properties
of the semiconductor layers. The extracted values in this
region enable quantification of contact and ohmic losses.
Noise Characteristics of the n-ZnO/p-Si
Heterostructure
It is now widely accepted that current noise
in semiconductors, metals, and electronic devices
originates primarily from resistance fluctuations [42].
These fluctuations may arise from variations in carrier
number, carrier mobility, or a combination of both. The
1/f noise spectrum emerges from the superposition of
elementary stochastic events characterized by a broad
distribution of time constants. In the McWhorter model,
noise is attributed to the tunneling of carriers between
the conducting channel and trap states in the oxide layer
[43], [44]. Examples of such elementary events include
changes in scattering cross-section due to carrier capture
or emission by trap states, tunneling transitions between
non-equivalent atomic configurations, and the motion of
dislocations and grain boundaries [45]. Each elementary
event is characterized by a specific time constant, and its
contribution to the noise spectral density is described
by a Lorentzian function. The relative contribution of
each noise mechanism to the total noise spectral density
depends on carrier concentration and the number of
active carriers involved. Generation-recombination
noise, arising from the capture and emission of charge
carriers, represents one such mechanism. Consequently,
Lorentzian-based noise relations are applicable only
in specific limiting cases and are not valid when the
dominant noise source is carrier mobility fluctuations.
In the case where the elementary event corresponds
to carrier capture and emission throughgeneration-
recombination noise at a localized energy level, the
expression for the noise spectral density is given by [46]
2
2 2
0
τ (1 )4( )
1 (2π τ)
t
I
N P PIS f
Vn f
⋅ ⋅ -
= ⋅
+
, (11)
where Nt is the trap concentration;
V is the sample volume;
P is the energy level occupancy.
As can be seen, the noise spectral density is
inversely proportional to the square of the free
electron concentration n₀ (∝ 1/n₀2). The noise spectral
density in this model is also expressed in terms of Nt,
the volumetric trap concentration given in units of
cm–3·eV–1. The total noise spectral density depends
on the thickness of the metal oxide active layer (Fig. 9
and Fig. 10), as well as on the total number of charge
carriers in the sample (Fig. 11).
Consider the practically important case of a
semiconductor resistor uniformly doped with shallow
impurities—specifically shallow donors (and acceptors)
at concentration Nt. At a given temperature, the shallow
level is fully ionized, and the equilibrium electron
concentration satisfies n₀ = Nt. In addition, a relatively
deep localized trap level is present at a concentration Nt.
Under thermal equilibrium, the rates of carrier capture
and emission are equal. When concentration fluctuations
are governed by a single trap type, the resulting noise
is of the generation-recombination type. However
multiple trap levels with a corresponding distribution of
characteristic time constants contribute collectively, 1/f
noise arises, and the concentration dependence of the
noise spectral density can deviate from the 1/n₀2 law.
For a simple two-level system, the standard theory
of generation-recombination noise assumes the existence
of a generation probability per unit time g(N) and a
recombination probability per unit time r(N), describing
transitions from the impurity level to the conduction
band and the reverse process, respectively, within
the framework of the detailed balance equation. In
Teсhnology and design in electronic equipment, 2026, N 126 ISSN 3083-6530 (Print)
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SENSORS
Fig. 9. Noise spectral characteristics of the n-ZnO/p-Si heterostructure for different ZnO absorber layer thicknesses dZnO:
1 — thermal noise; 2 — GR noise; 3 — 1/f noise; 4 — shot noise; 5 — total noise
Fig. 10. Noise spectral characteristics of the
n-ZnO/p-Si heterostructure with different
concentrations of electron traps in the ZnO
layer (cm–3):
1 — 1014; 2 — 1015; 3 — 1016; 4 — 1017;
5 — 1018
(layer thickness 300 nm)
a)
10–20
10–22
10–24
10–26
10–28
10–30
10–32
N
oi
se
d
en
si
ty
, V
2 /H
z
100 101 102 103 104 105 106
Frequency, Hz
2
3
4
1
5
dZnO = 50 nm
4
b)
10–20
10–22
10–24
10–26
10–28
10–30
10–32
N
oi
se
d
en
si
ty
, V
2 /H
z
100 101 102 103 104 105 106
Frequency, Hz
dZnO = 100 nm
2
3
1
5
c)
10–20
10–22
10–24
10–26
10–28
10–30
10–32
N
oi
se
d
en
si
ty
, V
2 /H
z
100 101 102 103 104 105 106
Frequency, Hz
dZnO = 200 nm
2
3
41
5
d)
10–20
10–22
10–24
10–26
10–28
10–30
10–32
N
oi
se
d
en
si
ty
, V
2 /H
z
100 101 102 103 104 105 106
Frequency, Hz
dZnO = 500 nm
2
3
41
5
10–17
10–18
10–19
10–20
10–21
10–22
N
oi
se
d
en
si
ty
, V
2 /H
z
1
2
3
4
5
10–1 100 101 102 103 104 105 106
Frequency, Hz
Teсhnology and design in electronic equipment, 2026, N 1 27ISSN 3083-6530 (Print)
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SENSORS
Fig. 11. Noise spectral characteristics of the n-ZnO/p-Si heterostructure for different concentrations of electron traps in the
ZnO layer Nt :
1 — thermal noise; 2 — GR noise; 3 — 1/f noise; 4 — shot noise; 5 — total noise
(layer thickness 300 nm)
Fig. 12. Octave software interface for simulating the noise power spectral density of the n-ZnO/p-Si heterostructure
4
a)
10–17
10–19
10–21
10–23
10–25
10–27
10–29
10–31
10–33
N
oi
se
d
en
si
ty
, V
2 /H
z
100 101 102 103 104 105 106
Frequency, Hz
Nt = 1013 cm–3
2
3
1
5
b)
10–18
10–20
10–22
10–24
10–26
10–28
10–30
10–32
N
oi
se
d
en
si
ty
, V
2 /H
z
100 101 102 103 104 105 106
Frequency, Hz
Nt = 1014 cm–3
2
3
4
5
1
c)
10–19
10–21
10–23
10–25
10–27
10–29
10–31
N
oi
se
d
en
si
ty
, V
2 /H
z
100 101 102 103 104 105 106
Frequency, Hz
Nt = 1015 cm–3
2
3
4
1
5
d)
10–20
10–22
10–24
10–26
10–28
10–30
N
oi
se
d
en
si
ty
, V
2 /H
z
100 101 102 103 104 105 106
Frequency, Hz
Nt = 1016 cm–3
2
3
4
5
1
4
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SENSORS
general, g is a monotonically decreasing function of N,
while r is a monotonically increasing function of N; the
exact forms of these functions are determined by the
physical process under consideration. Under steady-
state conditions, the balance between generation and
recombination is established at g₀ ≈ g (Nt) and r₀ ≈ r (Nt).
The values of g and r can be obtained by physically
modeling the respective generation and recombination
processes. Based on these calculations, the total noise
spectral density of the heterostructure can be estimated
numerically, for example using the Octave software
environment (Fig. 12).
Quantum Efficiency Characteristics
The QE of a photovoltaic cell is influenced by a range
of factors, including material properties, absorber layer
thickness, and fabrication quality, as illustrated in Fig. 13.
The photoresponse of the device is also strongly
dependent on the polarization state of the incident
illumination. The photodetector based on the optimized
heterojunction exhibits a broad spectral photoresponse
spanning the ultraviolet region. The results demonstrate
well-pronounced photodetection performance under
ultraviolet irradiation, while the photosensitivity de-
creases appreciably in the visible spectral region. The
high responsivity and on/off photocurrent ratio of the
ZnO/Si device are attributed to enhanced charge carrier
separation, facilitated by the interfacial coupling effect
between the ZnO thin film and the Si substrate.
Responsivity R and specific detectivity D* are the key
figures of merit for evaluating photodetector performance
and assessing detection sensitivity. Assuming that shot
noise originating from the dark current is the dominant
contribution to the total noise, R and D* can be expressed
as [47]:
Fig. 13. Spectral dependencies of the derivative of the reduced
quantum efficiency dQE/dλ in dark (1) and illuminated
(2) conditions (a), and responsivity (b) of the ZnO/Si
heterostructure
a)
FF, %
12
10
8
6
4
2
0 100 200 300 400 500 600 ZnO, nm
b)
(4.2)
3
2
1
0
–1
–2
–3
(–3.6)
Sp
ec
tra
l r
es
po
ns
iv
ity
, A
/W
300 400 500 600 700 800 900
Wavelength, nm
Fig. 14. Dependence of the fill factor FF (a), efficiency η (b),
quantum efficiency QE (c), and responsivity R (d) of the
n-ZnO/p-Si heterostructure on the thickness dZnO of the ZnO
absorbing layer
b)
η, %
70
60
50
40
30
0 100 200 300 400 500 600 dZnO, nm
c)
QE, %
80
60
40
20
0 100 200 300 400 500 600 dZnO, nm
d)
R, A/W
0.20
0.15
0.10
0.05
0 100 200 300 400 500 600 dZnO, nm
a)
0.04
0.02
0
–0.02
–0.04
–0.06
–0.08
(–0.11)
dQ
E/
dλ
, 1
/n
m
300 400 500 600 700 800 900
Wavelength, nm
1
2
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SENSORS
light
in
I
R
W A
= ; *
dark2
R AD
qI
= , (12)
where Win is the incident light intensity;
A is the effective area of the device;
q is the elementary charge (q = 1.60·10−19 C);
2q·Idark is the shot noise current density.
Under ultraviolet illumination, the achieved res-
ponsivity of the photodetector is 0.23 A/W, and the
specific detectivity is 1.1·1010 Jones (cm·Hz–1/2·W–1), as
shown in Fig. 13, b. The photovoltaic characteristics of the
n-ZnO/p-Si heterostructure as a function of ZnO absorber
layer thickness are presented in Fig. 14.
Conclusions
In this work, an n-ZnO/p-Si photodetector was
numerically simulated and optimized using software
SCAPS-1D. The simulated broadband ZnO/Si hetero-
junction photodetector exhibited a nonlinear increase in
dark current as a function of applied voltage, consistent
with the rectifying behavior of a p–n junction. The
optimized heterojunction photodetector demonstrates
a well-pronounced photoresponse across the spectral
range of 200 – 400 nm. Under illumination, the optimal
short-circuit current density reaches JSC = 13.9 mA/cm2,
and the open-circuit voltage is VOC ≈ 0.725 V.
The simulation methodology for characterizing
heterostructures is consistent with established standards.
It enables the systematic selection of absorber layer
thickness, electron affinity, and other electrophysical
parameters for each constituent layer. Variation of
the doping concentration in the absorber layer within
SCAPS-1D yields a range of photovoltaic responses
and responsivity values. Following optimization, the
photosensitivity of the device is governed by the interplay
between free carrier concentration and trap density. The
improvement in the external quantum efficiency profile
is primarily attributed to absorber layer optimization
and, additionally, to the applied reverse bias voltage.
The applied bias further enhances quantum efficiency
by promoting charge carrier injection driven by photon
absorption, as well as by the photon multiplication effect.
At a wavelength of 300 nm, the optimized fill factor
reaches 63.18%.
In summary, a self-powered photodetector based on the
n-ZnO/p-Si heterostructure was numerically investigated
and optimized using SCAPS-1D. The responsivity
and specific detectivity of the simulated device are
0.23 A/W and 1.1·1010 Jones, respectively. The simulation
results highlight the potential of n-ZnO/p-Si-based
optoelectronic devices and indicate a promising direction
for further development. Further research should be
directed toward the practical implementation and
experimental verification of the proposed photodetector
architecture.
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Received 31 March 2026
Accepted 19 June 2026
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Copyright: © 2026, The author(s). Licensee: Politekhperiodika, Odesa, Ukraine. This article is an open access
article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license
(https://creativecommons.org/licenses/by/4.0/).
Відомості про авторів
Ігор Вірт, докт. фіз.-мат. наук, професор, Дрогобицький
державний педагогічний університет імені Івана
Франка, Україна;
е-mail: isvirt@dspu.edu.ua;
ORCID: https://orcid.org/0000-0001-7200-6055
Іван Падалка, аспірант, Дрогобицький державний
педагогічний університет імені Івана Франка, Україна;
е-mail: ivan.padalka@dspu.edu.ua;
ORCID: https://orcid.org/0009-0007-4071-5878
About the authors
Ihor Virt, Dr. Sc, Professor, Ivan Franko State Pedagogical
University of Drohobych, Ukraine;
е-mail: isvirt@dspu.edu.ua;
ORCID: https://orcid.org/0000-0001-7200-6055
Ivan Padalka, Grad. Student, Ivan Franko State Pedagogical
University of Drohobych, Ukraine;
е-mail: ivan.padalka@dspu.edu.ua;
ORCID: https://orcid.org/0009-0007-4071-5878
Ігор ВІРТ, Іван ПАДАЛКА
Україна, Дрогобицький державний педагогічний університет
імені Івана Франка
МОДЕЛЮВАННЯ ФОТОДІОДНОЇ СТРУКТУРИ
НА ОСНОВІ ГЕТЕРОПЕРЕХОДУ ZnO/SI
У роботі чисельно досліджено та проаналізовано за допомогою програмного забезпечення Solar Cell Capacitance
Simulator in One-Dimension (SCAPS-1D) фотодетектор з власним живленням, який використовує об'ємний
n–p-гетероперехід n-ZnO/p-Si. SCAPS-1D — це числова платформа для аналізу та оптимізації тонкоплівкових
фотоелектричних гомо- та гетероперехідних структур за допомогою самоузгодженого розв'язання рівняння Пуассона
та рівнянь неперервності носіїв заряду, що дозволяє проводити детальний аналіз багатошарових гетеропереходів,
дозволяючи змінювати товщину шару, концентрацію легування, щільність дефектів та ширину забороненої зони.
Програмне забезпечення побудовано на числовому розв'язанні фундаментальних напівпровідникових рівнянь, а саме
рівняння Пуассона та рівнянь неперервності носіїв заряду, що забезпечує точне обчислення J–V характеристик та
квантової ефективності.
Досліджено енергетичні зони, залежність густини струму від напруги (J–V), спектральні характеристики
фоточутливості та детектуючу здатність в ультрафіолетовому діапазоні. Використовувалися різні параметри
для опису електронного транспорту у плівці ZnO. Оптимізацією підібрано товщину шарів ZnO та Si, які були
визначені на рівні 100 та 700 нм відповідно. Концентрація неглибокого донора шару ZnO змінювалась у межах
від 1014 до 1018 см−3. Моделювання засвідчило, що фотодетектор на основі гетеропереходу з оптимальними
параметрами характеризується значним фотовідгуком при опромінюванні ультрафіолетом із довжиною хвилі
300 нм. В умовах освітлення оптимальний струм короткого замикання досягає 13,9 мА/см², а напруга холостого
ходу — близько 0,725 В. Для ZnO як матеріалу електронного транспорту (ЕTM) отримано такі найкращі результати:
загальна ефективність η ≈ 7,71%, коефіцієнт заповнення FF ≈ 63,18%, струм короткого замикання JSC ≈ 13,9 мА/см²,
напруга холостого ходу VOC ≈ 0,725 В. Чутливість та детектувальна здатність змодельованого фотодетектора
становлять R = 0,23 А/Вт і D* = 1,1·1010 Джонс. Для покращення продуктивності фотодетекторів було досліджено
вплив товщини шарів, концентрації неглибоких донорів та густини дефектів. Отримані результати моделювання
свідчать про перспективність подальших досліджень у галузі оптоелектронних пристроїв на основі ZnO.
Ключові слова: фотоелемент, фотодетектор, числове моделювання, матеріал електронного транспорту (ЕТM),
ZnO, гетероструктура, програма SCAPS-1D.
DOI: 10.15222/TKEA2026.1.17
УДК 621.382.592
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| institution | Technology and design in electronic equipment |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-08-04T01:00:59Z |
| publishDate | 2026 |
| publisher | PE "Politekhperiodika", Book and Journal Publishers |
| record_format | ojs |
| resource_txt_mv | wwwtkeacomua/5d/16f578c9bb02c9da7a959279f0ccb65d.pdf |
| spelling | oai:tkea.com.ua:article-7972026-08-03T14:14:28Z Modeling of a photodiode structure based on a heterojunction ZnO/Si Моделювання фотодіодної структури на основі гетеропереходу ZnO/Si Virt, Ihor Padalka, Ivan photovoltaic cell photodetector numerical simulation electron transport material (ETM) ZnO heterostructure SCAPS-1D program фотоелемент фотодетектор числове моделювання матеріал електронного транспорту (ЕТM) ZnO гетероструктура програма SCAPS-1D In this work, a self-powered photodetector based on a bulk ZnO/Si p–n heterojunction is numerically investigated and analyzed using the Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D). The energy band diagram, electron-hole generation and recombination rates, current-voltage (J–V) characteristics, spectral photosensitivity response, and specific detectivity are examined. To optimize photodetector performance, the effects of absorber layer thickness, shallow acceptor and donor densities, and defect density were systematically studied. Various electron transport parameters of ZnO were also considered. The responsivity and specific detectivity of the simulated photodetector are 0.23 A/W and 1.1·1010 Jones, respectively. У роботі чисельно досліджено та проаналізовано за допомогою програмного забезпечення Solar Cell Capacitance Simulator in One-Dimension (SCAPS-1D) фотодетектор з власним живленням, який використовує об'ємний n–p-гетероперехід n-ZnO/p-Si. SCAPS-1D — це числова платформа для аналізу та оптимізації тонкоплівкових фотоелектричних гомо- та гетероперехідних структур за допомогою самоузгодженого розв'язання рівняння Пуассона та рівнянь неперервності носіїв заряду, що дозволяє проводити детальний аналіз багатошарових гетеропереходів, дозволяючи змінювати товщину шару, концентрацію легування, щільність дефектів та ширину забороненої зони. Програмне забезпечення побудовано на числовому розв'язанні фундаментальних напівпровідникових рівнянь, а саме рівняння Пуассона та рівнянь неперервності носіїв заряду, що забезпечує точне обчислення J–V характеристик та квантової ефективності. Досліджено енергетичні зони, залежність густини струму від напруги (J–V), спектральні характеристики фоточутливості та детектуючу здатність в ультрафіолетовому діапазоні. Використовувалися різні параметри для опису електронного транспорту у плівці ZnO. Оптимізацією підібрано товщину шарів ZnO та Si, які були визначені на рівні 100 та 700 нм відповідно. Концентрація неглибокого донора шару ZnO змінювалась у межах від 1014 до 1018 см−3. Моделювання засвідчило, що фотодетектор на основі гетеропереходу з оптимальними параметрами характеризується значним фотовідгуком при опромінюванні ультрафіолетом із довжиною хвилі 300 нм. В умовах освітлення оптимальний струм короткого замикання досягає 13,9 мА/см², а напруга холостого ходу — близько 0,725 В. Для ZnO як матеріалу електронного транспорту (ЕTM) отримано такі найкращі результати: загальна ефективність η ≈ 7,71%, коефіцієнт заповнення FF ≈ 63,18%, струм короткого замикання JSC ≈ 13,9 мА/см², напруга холостого ходу VOC ≈ 0,725 В. Чутливість та детектувальна здатність змодельованого фотодетектора становлять R = 0,23 А/Вт і D* = 1,1·1010 Джонс. Для покращення продуктивності фотодетекторів було досліджено вплив товщини шарів, концентрації неглибоких донорів та густини дефектів. Отримані результати моделювання свідчать про перспективність подальших досліджень у галузі оптоелектронних пристроїв на основі ZnO. PE "Politekhperiodika", Book and Journal Publishers 2026-06-30 Article Article Peer-reviewed Article application/pdf https://www.tkea.com.ua/index.php/journal/article/view/TKEA2026.1.17 10.15222/TKEA2026.1.17 Technology and design in electronic equipment; No. 1 (2026): Technology and design in electronic equipment; 17-31 Технологія та конструювання в електронній апаратурі; № 1 (2026): Технологія та конструювання в електронній апаратурі; 17-31 3083-6549 3083-6530 10.15222/TKEA2026.1 en https://www.tkea.com.ua/index.php/journal/article/view/TKEA2026.1.17/1226 Copyright (c) 2026 Ihor Virt, Ivan Padalka http://creativecommons.org/licenses/by/4.0/ |
| spellingShingle | фотоелемент фотодетектор числове моделювання матеріал електронного транспорту (ЕТM) ZnO гетероструктура програма SCAPS-1D Virt, Ihor Padalka, Ivan Моделювання фотодіодної структури на основі гетеропереходу ZnO/Si |
| title | Моделювання фотодіодної структури на основі гетеропереходу ZnO/Si |
| title_alt | Modeling of a photodiode structure based on a heterojunction ZnO/Si |
| title_full | Моделювання фотодіодної структури на основі гетеропереходу ZnO/Si |
| title_fullStr | Моделювання фотодіодної структури на основі гетеропереходу ZnO/Si |
| title_full_unstemmed | Моделювання фотодіодної структури на основі гетеропереходу ZnO/Si |
| title_short | Моделювання фотодіодної структури на основі гетеропереходу ZnO/Si |
| title_sort | моделювання фотодіодної структури на основі гетеропереходу zno/si |
| topic | фотоелемент фотодетектор числове моделювання матеріал електронного транспорту (ЕТM) ZnO гетероструктура програма SCAPS-1D |
| topic_facet | photovoltaic cell photodetector numerical simulation electron transport material (ETM) ZnO heterostructure SCAPS-1D program фотоелемент фотодетектор числове моделювання матеріал електронного транспорту (ЕТM) ZnO гетероструктура програма SCAPS-1D |
| url | https://www.tkea.com.ua/index.php/journal/article/view/TKEA2026.1.17 |
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