Optimum Concentration of InSb Photodiode for Minimum Low Reverse Bias Leakage Current
We have investigated a relation between the impurity concentration and the leakage current for three types of InSb diodes. They were fabricated with different impurity concentrations on both sides of the junction such as p - n, p^+ - n; and p^+ - n+ in order to achieve the minimal level of noise. It...
Збережено в:
| Дата: | 2010 |
|---|---|
| Автори: | , , , , , |
| Формат: | Стаття |
| Мова: | Англійська |
| Опубліковано: |
Відділення фізики і астрономії НАН України
2010
|
| Теми: | |
| Онлайн доступ: | https://nasplib.isofts.kiev.ua/handle/123456789/13432 |
| Теги: |
Додати тег
Немає тегів, Будьте першим, хто поставить тег для цього запису!
|
| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | Optimum Concentration of InSb Photodiode for Minimum Low Reverse Bias Leakage Current / M. Moradi, M. Daraee, M. Hajian, M.A. Forghani, M. Rastgoo, A.O. Alipour // Укр. фіз. журн. — 2010. — Т. 55, № 4. — С. 422-425. — Бібліогр.: 14 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859807213062717440 |
|---|---|
| author | Moradi, M. Daraee, M. Hajian, M. Forghani, M.A. Rastgoo, M. Alipour, A.O. |
| author_facet | Moradi, M. Daraee, M. Hajian, M. Forghani, M.A. Rastgoo, M. Alipour, A.O. |
| citation_txt | Optimum Concentration of InSb Photodiode for Minimum Low Reverse Bias Leakage Current / M. Moradi, M. Daraee, M. Hajian, M.A. Forghani, M. Rastgoo, A.O. Alipour // Укр. фіз. журн. — 2010. — Т. 55, № 4. — С. 422-425. — Бібліогр.: 14 назв. — англ. |
| collection | DSpace DC |
| description | We have investigated a relation between the impurity concentration and the leakage current for three types of InSb diodes. They were fabricated with different impurity concentrations on both sides of the junction such as p - n, p^+ - n; and p^+ - n+ in order to achieve the minimal level of noise. It is shown that the leakage current at a low reverse bias has a minimum for the p^+ - n diode structure (impurity concentration of order of 2х10^15 cm^-3 for the n-type and 1х10^18 cm^-3 for the p-type). Increasing the impurity beyond these values may cause the tunneling at a low reverse bias voltage close to zero, and decreasing the impurity causes increasing the diffusion current.
Дослiджено зв’язок мiж концентрацiєю домiшки та струму витоку для трьох типiв InSb дiодiв. Дiоди було виготовлено з рiзними концентрацiями домiшки на обох боках перехода, а саме p - n, p^+ - n та p^+ - n^+; щоб отримати найнижчий рiвень шумiв. Показано, що струм витоку має мiнiмальне значення при низьких зворотних напругах змiщення для p^+ - n структури (концентрацiя домiшки порядку 2 х 10^15 cм^-3 для n-типу та 1 х 10^18 cм^-3 для p-типу). Зростання концентрацiї домiшки понад цих значень може викликати тунелювання при малих зворотних напругах змiщення, тодi як при зменшеннi концентрацiї зростає дифузiйний струм.
|
| first_indexed | 2025-12-07T15:17:17Z |
| format | Article |
| fulltext |
M. MORADI, M. DARAEE, M. HAJIAN et al.
OPTIMUM CONCENTRATION OF InSb PHOTODIODE
FOR MINIMUM LOW REVERSE BIAS
LEAKAGE CURRENT
M. MORADI, M. DARAEE, M. HAJIAN, M.A. FORGHANI, M. RASTGOO,
A.O. ALIPOUR
Semiconductor Component Industry
(P.O. Box 19575-199, Tehran, Iran)
PACS 71.20.Nr, 71.55.Eg
c©2010
We have investigated a relation between the impurity concentra-
tion and the leakage current for three types of InSb diodes. They
were fabricated with different impurity concentrations on both
sides of the junction such as p− n, p+ − n, and p+ − n+ in order
to achieve the minimal level of noise. It is shown that the leakage
current at a low reverse bias has a minimum for the p+ − n diode
structure (impurity concentration of order of 2×1015 cm−3 for the
n-type and 1×1018 cm−3 for the p-type). Increasing the impurity
beyond these values may cause the tunneling at a low reverse bias
voltage close to zero, and decreasing the impurity causes increas-
ing the diffusion current.
1. Introduction
InSb photodiode is one of the most useful and appli-
cable detectors at 3–5 µm wavelength [1]. These de-
tectors have different applications in military, medical,
and aerospace industries [2, 3]. In a qualified detector,
the lower leakage current is essential in decreasing the
noise and increasing the detectivity [4]. In photodiodes,
the shot noise is a dominant noise at the near-zero re-
verse bias [5]. With regard for the shot noise relation (1)
which is directly related to the current passing through a
diode, minimizing the leakage current will minimize the
shot and consequently detector noises [6]:
i2shot = 2eIdcΔf. (1)
Here, Idc is the dc current flowing through the diode,
and Δf is the electric bandwidth. The aim of this ar-
ticle is to minimize the leakage current at low reverse
biases in order to achieve the minimal level of noises.
The leakage current (J0) is the sum of the diffusion
current (Jd), generation-recombination (Jg−r), parallel
shunt (Js), and tunneling (Jt) ones [7]:
J = Jd + Jg−r + JT + Js. (2)
The diffusion current is due to the carrier generation-
recombination outside the depletion region. The amount
of this current is dependent on the carrier concentra-
tion on both sides of the junction; the increasing carrier
concentration at both sides of the junction will cause
decreasing this current. The generation-recombination
current (g − r) is determined by traps in the depletion
region. For example, the g-r current in an InSb photo-
diode is given by the relation [8]
Jgen ∝ T 3/2 exp
(
− Eg
2KT
)
(Vbi − V )1/2, (3)
where Vbi is the built-in potential, and V is the applied
bias. The shunt current is characterized by a linear I−V
characteristics. This current is caused by the current
leakage at the junction-edge surface and is proportional
to the temperature, energy gap, and bias voltage [8]:
Jsh ∝ V T 3/2 exp
(
− Eg
2KT
)
. (4)
Proper anodic oxides at the surface of the formed junc-
tion which contains few accumulated charges are very
crucial to a decrease in this current. The tunneling cur-
rent is a result of the thin potential barrier. A very high
carrier concentration at both sides of the junction will
cause the electrons to directly tunnel across the junction
from the valence band to the conduction band (the band-
to-band tunneling (BTB)) or to indirectly tunnel across
the junction by intermediate trap states in the junc-
tion region (trap-assisted tunneling (TAT)). The band-
to-band tunneling originates under the influence of a rel-
atively high reverse bias but the TAT process occurs at
a lower field than BTB. In comparison with BTB, TAT
is critically dependent not only on the doping concen-
tration but also on the density of recombination in the
band gap [13]. The direct tunneling current in InSb is
given by the relation [8]
JT = K1(Vbi − V )
(
V 2
T
)
exp
(
−K2
(Vbi − V )1/2
)
, (5)
where K1 and K2 are constants with respect to V and T .
422 ISSN 2071-0194. Ukr. J. Phys. 2010. Vol. 55, No. 4
OPTIMUM CONCENTRATION OF InSb PHOTODIODE
2. Fabrication Process
The p−n, p+−n, and p+−n+ photodiodes considered in
this study are fabricated on two different single-crystal
n-type 〈111〉 Te-doped InSb substrates with concentra-
tion of n+ (1 × 1018 cm−3) and n (2 × 1015 cm−3).
To fabricate p − n and p+ − n junction diodes, the
closed-tube thermal diffusion is used for the Cd diffu-
sion into the n substrate to levels of 5 × 1016 cm−3
and 3 × 1018 cm−3. For a p+ − n+ junction, the LPE
method was applied to attain p+ = (2 × 1019 cm−3) on
the n+ substrate. The thickness of wafers is 500 µm,
and that of the p-type layer is 5 µm. For this purpose,
the wafers were initially cleaned by organic solvents and
CP4A (HNO3 : CH3 − COOH : HF : H2O at 2:1:1:10)
etchant [9]. The further cleaning was done by buffer HF
followed by a long rinse in DI water and dried using a
nitrogen gun [10]. Diffused impurity concentrations have
been measured using the Hall effect. The mesostructure
of a diode was constructed by using photolithography
and etching in (HF : H2O2 : H2O at 1:1:4) solution [12].
The etched region was anodized in a 0.1-N KOH solu-
tion by a constant current source, and then a 4000-Å
SiO layer was coated to improve the anode oxide sta-
bility. Finally, Pt/Cr/Au and Cr/Au layers used as an
ohmic contact were deposited, respectively, on the p- and
n-type substrates. The total sensitive area of the diodes
is 1 mm2. A cross-sectional view of the detector test
structure is illustrated in Fig. 1.
3. Results and Discussion
In order to identify the dark current at the correspond-
ing bias, the diodes fabricated were analyzed, by using
the KEITHLEY 236 I − V characteristic at 77 K (LN2)
which is the working temperature of InSb photodiodes.
The devices were cover by a cold metal shield after the
installation on a Dewar. The current-voltage character-
istics for the forward and reverse biases of three different
fabricated photodiodes p − n, p+ − n, and p+ − n+ are
shown in Fig. 2,a and 2,b, respectively.
In these graphs, three main regions of the I−V curve
(near the zero, forward, and reverse biases are shown.
The results are tabulated in Table. Comparing these
Comparison of parameters of three different InSb IR de-
tectors
Nd Na Vbi I−0.1 I−3
p+ − n+ 3× 1018 2× 1019 178 · 4 mv −22 mA � −100 mA
p+ − n 2× 1015 1× 1018 128 mv −1 · 99 nA −96 · 24 µA
p− n 2× 1015 5× 1016 116 mv −7 · 12 nA −4 · 23 µA
Fig. 1. Schematic of a fabricated InSb diode and a cooled test
structure
diodes at the forward bias, we see that the built-in volt-
age and the zero bias dark current for p+−n+ are higher
than those for the other two because of a higher impurity
concentration.
The nature of the excess current of InSb photodiodes
at the forward biases V < 0.05 is not known exactly, but
it is seen that, at low reverse and forward biases, TAT
and shunt components are the dominant components of
the dark current, and the excess current is due to the
TAT current [14]. The consideration of the tangent of
the current at a reverse bias shows that, at p+ − n+
due to a high impurity concentration (high field) and
the exceeding degeneracy level, we have a BTB tunnel-
ing current at very low reverse bias voltages (also at
zero). According to relation (5), at the increasing re-
verse bias, the current rate will increase exponentially,
and a rapid breakdown will occur. But, in both p − n
and p+ − n due to a lower impurity concentration, the
interband tunneling will appear at higher reverse biases
(that appears for p+− n at V < −0.3). The rate of cur-
rent increase at a reverse bias is very low, and we have
a soft breakdown. Since PV-InSb infrared detectors are
usually used at a reverse bias very close to zero (0–300
mV) [11], the investigation of the leakage current of a
detector at reverse biases close to zero is more impor-
tant with respect to other two regions. The comparison
of leakage currents near zero bias shows that the least
leakage current is related to a p+−n diode. The diffusion
current, generation-recombination, and TAT are domi-
nant at low reverse biases, and they are optimum for the
p+ − n structure. At p− n diode due to a low impurity
concentration, the diffusion and g-r currents increase at
low reverse biases, since the BTB tunneling current ap-
pears at more reverse biases. The dark current of the
p−n structure at high reverse biases is lower than those
of p+ − n and p+ − n+ due to a high impurity concen-
tration, and the BTB and TAT tunneling currents are
considerable even at zero bias.
ISSN 2071-0194. Ukr. J. Phys. 2010. Vol. 55, No. 4 423
M. MORADI, M. DARAEE, M. HAJIAN et al.
Fig. 2. Current-voltage curves of p+−n+, p+−n, and p−n InSb photodiodes at 77 K: (a) – semilog current-voltage curves for forward
bias voltages, and (b) – log-log current-voltage curves for reverse bias voltages
4. Conclusion
Because a low noise is of great importance in infrared
detectors and due to its direct relation to the leakage
current, it is essential to decrease the leakage current
as much as possible. In this respect, the selection of
a proper substrate with minimum crystal defects is of
crucial meaning. In performing the fabrication with a
proper anodic oxide at the edges of a junction, the selec-
tion of a precise doping on both sides is of main priority.
The experimental results show that a very high impurity
concentration will cause the BTB tunneling current at
a reverse bias close to zero (working bias of InSb pho-
todiodes). In a p − n diode due to a low impurity con-
centration, the diffusion and g-r currents increase. On
the other hand, introducing the impurity at the degen-
eracy boundary of the p+ − n structure (impurity con-
centrations are of the order of 2 × 1015 cm−3 for the
n-type and 1 × 1018 cm−3 for the p-type) is the opti-
mum case. By selecting the impurity and approaching
the bias to zero with the minimum leakage current, we
can obtain the minimum noise and the highest detectivi-
ty.
The authors would like to thank Gh.R. Valizadeh and
M.H. Saani for their stimulating discussions, helpful sug-
gestions, and the technical assistance.
1. I. Bloom and Ya. Nemirovsky, IEEE Trans. Electron Dev.
39 (4) (1992).
2. A.M. Fowler, J.B. Heynssens et al., SPIE 1946, 667
(1993).
3. A. Rogalski, in Proceedings of the Symposium on Pho-
tonics Technologies for 7th Framework Program, edited
by A. Popiolek-Masajada (Polytechn. Wroclaw, Wroclaw,
2006), p. 137.
4. A. Rogalski and M. Razeghi, SPIE 3287, 1 (1998).
5. E.L. Dereniak, Infrared Detectors and Systems (Wiley,
New York, 1996).
6. R.D. Hudson, jr., Infrared System Engineering (Wiley,
New York, 2006).
7. J.P. Prineasa, B.M. Maiorovd et al., SPIE 6119, 1
(2006).
8. F.K. Hopkins and J.T. Boyd, Infrared Phys. 24, 391
(1984).
9. H. Simchi, S. Bahreani, and M.H. Saani, EJP-AP 33, 1
(2006).
424 ISSN 2071-0194. Ukr. J. Phys. 2010. Vol. 55, No. 4
OPTIMUM CONCENTRATION OF InSb PHOTODIODE
10. I. Bloom and Ya. Nemirovsky, IEEE Trans. Electron Dev.
40 309 (1993).
11. G. Gaussorgues, Infrared Thermography (Chapman and
Hall, London, 1994).
12. M. Daraee, M. Moradi, M. Hajian, M. Rastgoo, and
M.A. Forghani, Electron. Lett. 45, 957 (2009).
13. Umid Tumkaya, Performance Assessment of Indium An-
timonide Photodetectors on Silicon Substrates. Thesis for
the degree of Master of Science( Middle East Technical
University, 2003).
14. A. Rogalski, Infrared Detectors (Gordon and Breach,
Amsterdam, 2000).
Received 25.04.09
ОПТИМАЛЬНА КОНЦЕНТРАЦIЯ ДОМIШКИ В InSb
ФОТОДIОДАХ З МIНIМАЛЬНИМ СТРУМОМ ВИТОКУ
ПРИ НИЗЬКIЙ ЗВОРОТНIЙ НАПРУЗI ЗМIЩЕННЯ
М. Морадi, М. Дараi, М. Хаджян,
М.А. Форганi, М. Растгу, А.О. Алiпур
Р е з ю м е
Дослiджено зв’язок мiж концентрацiєю домiшки та струму ви-
току для трьох типiв InSb дiодiв. Дiоди було виготовлено з
рiзними концентрацiями домiшки на обох боках перехода, а
саме p − n, p+ − n та p+ − n+, щоб отримати найнижчий рi-
вень шумiв. Показано, що струм витоку має мiнiмальне зна-
чення при низьких зворотних напругах змiщення для p+ − n
структури (концентрацiя домiшки порядку 2 · 1015 cм−3 для
n-типу та 1 · 1018 cм−3 для p-типу). Зростання концентрацiї
домiшки понад цих значень може викликати тунелювання при
малих зворотних напругах змiщення, тодi як при зменшеннi
концентрацiї зростає дифузiйний струм.
ISSN 2071-0194. Ukr. J. Phys. 2010. Vol. 55, No. 4 425
|
| id | nasplib_isofts_kiev_ua-123456789-13432 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 2071-0194 |
| language | English |
| last_indexed | 2025-12-07T15:17:17Z |
| publishDate | 2010 |
| publisher | Відділення фізики і астрономії НАН України |
| record_format | dspace |
| spelling | Moradi, M. Daraee, M. Hajian, M. Forghani, M.A. Rastgoo, M. Alipour, A.O. 2010-11-08T17:19:31Z 2010-11-08T17:19:31Z 2010 Optimum Concentration of InSb Photodiode for Minimum Low Reverse Bias Leakage Current / M. Moradi, M. Daraee, M. Hajian, M.A. Forghani, M. Rastgoo, A.O. Alipour // Укр. фіз. журн. — 2010. — Т. 55, № 4. — С. 422-425. — Бібліогр.: 14 назв. — англ. 2071-0194 PACS 71.20.Nr, 71.55.Eg https://nasplib.isofts.kiev.ua/handle/123456789/13432 We have investigated a relation between the impurity concentration and the leakage current for three types of InSb diodes. They were fabricated with different impurity concentrations on both sides of the junction such as p - n, p^+ - n; and p^+ - n+ in order to achieve the minimal level of noise. It is shown that the leakage current at a low reverse bias has a minimum for the p^+ - n diode structure (impurity concentration of order of 2х10^15 cm^-3 for the n-type and 1х10^18 cm^-3 for the p-type). Increasing the impurity beyond these values may cause the tunneling at a low reverse bias voltage close to zero, and decreasing the impurity causes increasing the diffusion current. Дослiджено зв’язок мiж концентрацiєю домiшки та струму витоку для трьох типiв InSb дiодiв. Дiоди було виготовлено з рiзними концентрацiями домiшки на обох боках перехода, а саме p - n, p^+ - n та p^+ - n^+; щоб отримати найнижчий рiвень шумiв. Показано, що струм витоку має мiнiмальне значення при низьких зворотних напругах змiщення для p^+ - n структури (концентрацiя домiшки порядку 2 х 10^15 cм^-3 для n-типу та 1 х 10^18 cм^-3 для p-типу). Зростання концентрацiї домiшки понад цих значень може викликати тунелювання при малих зворотних напругах змiщення, тодi як при зменшеннi концентрацiї зростає дифузiйний струм. The authors would like to thank Gh.R. Valizadeh and M.H. Saani for their stimulating discussions, helpful suggestions, and the technical assistance. en Відділення фізики і астрономії НАН України Тверде тіло Optimum Concentration of InSb Photodiode for Minimum Low Reverse Bias Leakage Current Оптимальна концентрація домішки в InSb фотодіодах з мінімальним струмом витоку при низькій зворотній напрузі зміщення Article published earlier |
| spellingShingle | Optimum Concentration of InSb Photodiode for Minimum Low Reverse Bias Leakage Current Moradi, M. Daraee, M. Hajian, M. Forghani, M.A. Rastgoo, M. Alipour, A.O. Тверде тіло |
| title | Optimum Concentration of InSb Photodiode for Minimum Low Reverse Bias Leakage Current |
| title_alt | Оптимальна концентрація домішки в InSb фотодіодах з мінімальним струмом витоку при низькій зворотній напрузі зміщення |
| title_full | Optimum Concentration of InSb Photodiode for Minimum Low Reverse Bias Leakage Current |
| title_fullStr | Optimum Concentration of InSb Photodiode for Minimum Low Reverse Bias Leakage Current |
| title_full_unstemmed | Optimum Concentration of InSb Photodiode for Minimum Low Reverse Bias Leakage Current |
| title_short | Optimum Concentration of InSb Photodiode for Minimum Low Reverse Bias Leakage Current |
| title_sort | optimum concentration of insb photodiode for minimum low reverse bias leakage current |
| topic | Тверде тіло |
| topic_facet | Тверде тіло |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/13432 |
| work_keys_str_mv | AT moradim optimumconcentrationofinsbphotodiodeforminimumlowreversebiasleakagecurrent AT daraeem optimumconcentrationofinsbphotodiodeforminimumlowreversebiasleakagecurrent AT hajianm optimumconcentrationofinsbphotodiodeforminimumlowreversebiasleakagecurrent AT forghanima optimumconcentrationofinsbphotodiodeforminimumlowreversebiasleakagecurrent AT rastgoom optimumconcentrationofinsbphotodiodeforminimumlowreversebiasleakagecurrent AT alipourao optimumconcentrationofinsbphotodiodeforminimumlowreversebiasleakagecurrent AT moradim optimalʹnakoncentracíâdomíškivinsbfotodíodahzmínímalʹnimstrumomvitokuprinizʹkíizvorotníinapruzízmíŝennâ AT daraeem optimalʹnakoncentracíâdomíškivinsbfotodíodahzmínímalʹnimstrumomvitokuprinizʹkíizvorotníinapruzízmíŝennâ AT hajianm optimalʹnakoncentracíâdomíškivinsbfotodíodahzmínímalʹnimstrumomvitokuprinizʹkíizvorotníinapruzízmíŝennâ AT forghanima optimalʹnakoncentracíâdomíškivinsbfotodíodahzmínímalʹnimstrumomvitokuprinizʹkíizvorotníinapruzízmíŝennâ AT rastgoom optimalʹnakoncentracíâdomíškivinsbfotodíodahzmínímalʹnimstrumomvitokuprinizʹkíizvorotníinapruzízmíŝennâ AT alipourao optimalʹnakoncentracíâdomíškivinsbfotodíodahzmínímalʹnimstrumomvitokuprinizʹkíizvorotníinapruzízmíŝennâ |