The injection photo diode on the basis of nSi-nCdS-n⁺CdS heterostructures
It is shown that the nSi-nCdS-n⁺CdS heterostructures in operative (carrying) direction of current, while being exposed to low intensity radiation, operate as injection photodiodes. Their current sensitivity is Sλ ≈ 2.12 A/W at λ = 0.625 µm, which effectively represents a 4.2 increase in compare...
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| Zitieren: | The injection photo diode on the basis of nSi-nCdS-n⁺CdS heterostructures / I.B. Sapaev // Физическая инженерия поверхности. — 2013. — Т. 11, № 3. — С. 260–262. — Бібліогр.: 5 назв. — англ. |
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irk-123456789-1003092016-05-20T03:03:05Z The injection photo diode on the basis of nSi-nCdS-n⁺CdS heterostructures Sapaev, I.B. It is shown that the nSi-nCdS-n⁺CdS heterostructures in operative (carrying) direction of current, while being exposed to low intensity radiation, operate as injection photodiodes. Their current sensitivity is Sλ ≈ 2.12 A/W at λ = 0.625 µm, which effectively represents a 4.2 increase in compare to spectral sensitivity of the ideal photo receiver at small wavelength of irradiation. Показано, что гетероструктуры nSi-nCdS-n⁺CdS в пропускном направлении тока при малых уровнях освещения работают как инжекционный фотодиод. Они обладают токовой чувствительностью Sλ ≈ 2.12 A/W при λ = 0.625 µm, что в 4.2 раза превышает спектральную чувствительность идеального фотоприемника при этой длине волны излучения. Высокие значения Sλ обеспечивают высокую эффективность превращения световой энергии в электрическую при малых уровнях освещенности. Показано, що гетероструктури nSі-nCdS-n⁺CdS у пропускному напрямку струму при малих рівнях освітлення працюють як інжекційний фотодіод. Він має струмову чутливість Sλ ≈ 2.12 A/W при λ = 0.625 µm, що в 4.2 разів перевищує спектральну чутливість ідеального фотоприймача при цій довжині хвилі випромінювання. Високізначення Sл забезпечують високу ефективність перетворення світлової енергії в електричну при малих рівнях освітленості. 2013 Article The injection photo diode on the basis of nSi-nCdS-n⁺CdS heterostructures / I.B. Sapaev // Физическая инженерия поверхности. — 2013. — Т. 11, № 3. — С. 260–262. — Бібліогр.: 5 назв. — англ. 1999-8074 http://dspace.nbuv.gov.ua/handle/123456789/100309 53.043;53.023;539.234. en Физическая инженерия поверхности Науковий фізико-технологічний центр МОН та НАН України |
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It is shown that the nSi-nCdS-n⁺CdS heterostructures in operative (carrying) direction of current,
while being exposed to low intensity radiation, operate as injection photodiodes. Their current sensitivity
is Sλ ≈ 2.12 A/W at λ = 0.625 µm, which effectively represents a 4.2 increase in compare to spectral
sensitivity of the ideal photo receiver at small wavelength of irradiation. |
| format |
Article |
| author |
Sapaev, I.B. |
| spellingShingle |
Sapaev, I.B. The injection photo diode on the basis of nSi-nCdS-n⁺CdS heterostructures Физическая инженерия поверхности |
| author_facet |
Sapaev, I.B. |
| author_sort |
Sapaev, I.B. |
| title |
The injection photo diode on the basis of nSi-nCdS-n⁺CdS heterostructures |
| title_short |
The injection photo diode on the basis of nSi-nCdS-n⁺CdS heterostructures |
| title_full |
The injection photo diode on the basis of nSi-nCdS-n⁺CdS heterostructures |
| title_fullStr |
The injection photo diode on the basis of nSi-nCdS-n⁺CdS heterostructures |
| title_full_unstemmed |
The injection photo diode on the basis of nSi-nCdS-n⁺CdS heterostructures |
| title_sort |
injection photo diode on the basis of nsi-ncds-n⁺cds heterostructures |
| publisher |
Науковий фізико-технологічний центр МОН та НАН України |
| publishDate |
2013 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/100309 |
| citation_txt |
The injection photo diode on the basis of nSi-nCdS-n⁺CdS heterostructures / I.B. Sapaev // Физическая инженерия поверхности. — 2013. — Т. 11, № 3. — С. 260–262. — Бібліогр.: 5 назв. — англ. |
| series |
Физическая инженерия поверхности |
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AT sapaevib theinjectionphotodiodeonthebasisofnsincdsncdsheterostructures AT sapaevib injectionphotodiodeonthebasisofnsincdsncdsheterostructures |
| first_indexed |
2025-07-07T08:38:42Z |
| last_indexed |
2025-07-07T08:38:42Z |
| _version_ |
1836976726130819072 |
| fulltext |
260
Injection photodiodes based on n+-n transitions
or Schottky barrier are normally made of high re-
sistance semiconductors characterized by large
length of diffusive displacement, whereas thickness
of the base area (distance from the injected contact
to the second one) tremendously exceeds (several
times) the diffusive displacement length − “long dio-
des” [1]. Such type photodiodes operate in the mo-
de of high levels of injection. The carrying capacity
of their base area is determined by injected carriers.
The injection photodiodes are developed and inve-
stigated on various types of semiconductors (doped
Germanium and Silicon, Gallium Arsenide and In-
dium Antimonide, solid alloys of A2B5 compounds
and other materials) [2]. However, there is virtually
no information in the literature on how to develop
injection photodiodes based on Si-CdS hetero-
structures. Such structures are characterized by
astonishing interrelation of electrical and photo-
electrical properties both of pertinent Si and CdS.
Such structures are characterized also by direct
optical transitions that help to obtain a high efficiency
of generation of electron-hole pairs.
The photosensitive n+CdS-nCdS-nSi structure
has been created by dusting of CdS-powders (in
quasi-closed system in vacuum 10−5 torr) on the sur-
face of silicon plate of n-type with the specific res-
istance ρ ≈ 15 Ohm⋅cm and thickness of 300 −
400 мm. Thus the source temperature was (CdS)
Tsource ≈ 800 − 850 °С, and on the substrate (nSi) it
was supported in limits ≈ 250 − 270 °С. The carried
out researches by means of microscope MII-4 have
shown, that films CdS consist of columnar grains to
be focused in the direction of the films growth and
disarranged on an azimuth. It has been established,
that the size of crystallites strongly depends on
technological modes and first of all on temperature
of Si substrate. For example, made at Tsubstrate=
УДК 53.043;53.023;539.234.
THE INJECTION PHOTO DIODE ON THE BASIS OF nSi-nCdS-n+CdS
HETEROSTRUCTURES
I.B. Sapaev
Physical Technical Institute of the Academy of Sciences of the Republic of Uzbekistan (Tashkent)
Uzbekistan
Received 02.07.2013
It is shown that the nSi-nCdS-n+CdS heterostructures in operative (carrying) direction of current,
while being exposed to low intensity radiation, operate as injection photodiodes. Their current sensitivity
is Sλ ≈ 2.12 A/W at λ = 0.625 µm, which effectively represents a 4.2 increase in compare to spectral
sensitivity of the ideal photo receiver at small wavelength of irradiation.
Keywords: heterostructure, film, spectrum, injection.
ИНЖЕКЦИОННЫЙ ФОТОДИОД НА ОСНОВЕ nSi-nCdS-n+CdS
ГЕТЕРОСТРУКТУРЫ
И.Б. Сапаев
Показано, что гетероструктуры nSi-nCdS-n+CdS в пропускном направлении тока при малых
уровнях освещения работают как инжекционный фотодиод. Они обладают токовой чувствите-
льностью Sλ ≈ 2.12 A/W при λ = 0.625 µm, что в 4.2 раза превышает спектральную чувствитель-
ность идеального фотоприемника при этой длине волны излучения. Высокие значения Sλ обе-
спечивают высокую эффективность превращения световой энергии в электрическую при малых
уровнях освещенности.
Ключевые слова: гетероструктура, пленка, спектр, инжекционный.
ІНЖЕКЦІЙНИЙ ФОТОДІОД НА ОСНОВІ nSі-nCdS-n+CdS ГЕТЕРОСТРУКТУРИ
І.Б. Сапаєв
Показано, що гетероструктури nSі-nCdS-n+CdS у пропускному напрямку струму при малих
рівнях освітлення працюють як інжекційний фотодіод. Він має струмову чутливість Sλ ≈ 2.12
A/W при λ = 0.625 µm, що в 4.2 разів перевищує спектральну чутливість ідеального фото-
приймача при цій довжині хвилі випромінювання. Високі значення Sл забезпечують високу ефек-
тивність перетворення світлової енергії в електричну при малих рівнях освітленості.
Ключові слова: гетероструктура, плівка, спектр, инжекційний.
Sapaev I.B., 2013
261ФІП ФИП PSE, 2013, т. 11, № 3, vol. 11, No. 3
250 °С films CdS had the size of crystallites ≈0,8 –
1 мm which completely penetrated all thickness of
films d ≈1 µm. Thus, grown up CdS films were high-
resistant with specific resistance ρ ≥ 108 Ohm⋅сm.
Further, on CdS film was formed n+CdS layer by
thickness ∼ 500 C and current-collecting “П” −
figurative contact by means of vacuum evaporation
In.
The spectral distribution of the photocurrent of
such structure consists of two parts and its spectral
range stretches from λ ≈ 460 nm to λ ≈ 1200 nm
(fig. 1). In the first and the second parts of spectral
distribution the photocurrent has different polarity
that is caused with return inclusion of the barriers
created between n+CdS-nCdS and nCdS-nSi.
Besides the curve of spectral distribution of
photosensitivity shows, that between sulphide of
cadmium and of silicon with electronic conductivity
is available an isotype heterojunction containing a
small density of superficial conditions on section
border. Acknowledgement to that is that the structure
has the straightening factor of more than two orders,
and occurrence of maximum in curve dependence
I/Io, λ at λ ≈ 955 nm; and tangent, made to it on re-
cession in long-wave area of the spectrum cuts on
abscissa axis the length of the wave, corresponding
to width of the forbidden zone of silicon.
The developed n+CdS-nCdS-nSi − hetero-
structure is characterized by rectification properties,
whereas the rectification coefficient defined as a ratio
of direct and reverse current at fixed voltage −
K = Iforward/Iback (V = 5 V) makes up 2 orders (refer
to fig. 2). The direct direction of current in the struc-
ture is deemed to occur when “+” potential is applied
on the contact of Silicon surface whereas “−” pote-
ntial is applied on the reverse surface. The analysis
of the direct line of dark current-voltage of n+CdS-
nCdS-nSi heterostructures [3] clearly demonstrates
that the base of the structure is of high-resistance
and the ratio of thickness of base to the length of
diffusion of the minority current carriers amounts
∼ 4 at base thickness of (nCdS) ∼ 1 µm, that corres-
ponds to the diffusive length of minor carriers –
electrons 0.26 µm. Thus, it is determined that
n+CdS-nCdS-nSi −−−−− heterostructures meet the re-
quirements set out for injection photodiodes [4].
Besides, the structure investigated is photo-sensitive.
Research of their current-voltage characteristics
in direct and reverse directions shows that there is
the strengthening of photocurrent. As one can judge
from fig. 3, the direct line of current-voltage cha-
racteristics obtained in darkness and while exposed
to light, practically do not differ from one another
judging by the shape of the line. However, the values
of photocurrent and dark current do indeed differ.
Comparing values of photocurrent and dark
current was done at the same voltage (V = 10 V).
They are reflected in tabl. 1. This table also reflects
Fig. 1. Spectral distribution of a photocurrent of n+CdS-
nCdS-nSi heterostructure.
Fig. 2. Conventional direct (1) and reverse (2) sections of
current-voltage characteristics of nSi-nCdS-n+CdS hetero-
structure in semi-log scale at room temperatures.
Fig. 3. Dark and light current-voltage line of nSi-nCdS-
n+CdS heterostructure: 1– dark, 2 – 0.05 Lux, 3 –1.25 Lux,
4 – 4 Lux, 5 – 20 mW/cm2.
I.B. SAPAEV
262
the photocurrent values and the current sensitivity
(Scurrent sensitivity) at different levels of illumination
(Е, lux). The data in the tabl. 1 clearly demonstrates
that the integrated sensitivity in the investigated
heterostructures has a high value. Moreover, it has
a maximum value at luminous flux of Е = 0.05 Lux,
wherby Scurrent sensitivity= 3720 A/Lm. For comparison
we should mark that the best industrial photo
receivers FD-7, FD-11 are characterized by
Scurrent sensitivity = (4 − 5) mA/lm [5].
Nevertheless, the current sensitivity still remains
high even at illumination with monochromatic light
of laser with the wavelength of λ = 0.625 µm and
power of 20 mW/cm2 , reaching ∼ 2.1 A/W. One
can incidentally conclude that we are actually
witnessing the photocurrent strengthening. This is
further evidenced by the fact that the current sen-
Таble 1
Dependences of the photocurrent (IPh) and
integrated sensitivity (Scurrent sensitivity) from light
exposure (Elux)
Е,
10–2 lux
Idark,
mА/cm2
IPh,
mА/cm2
Scurrent sensitivity,
А/lm
Scurrent sensitivity,
А/W
0 0.91 – – –
5 – 18.6 4.1·1053720
125 – 20.5 1.8·104164
400 – 22 6·10355
sitivity of such structure tends to be ≈2.1 A/W,
whereas the ideal photo receiver at similar wave-
length has the current sensitivity of ≈0.5 A/W [5].
Under the ideal photo device, we understand the
one, which is free of effect of reflection from surface,
has the internal quantum efficiency ≈1 and all gene-
rated carriers participate in the process of photo-
current formation. Usually such photo receivers are
absent as they are idealized. That is why it is possible
to think that nSi-nCdS-n+CdS – heterostructure has
high spectrum sensitivity in the result of inner stren-
gthening of photocurrent.
REFERENCES
1. Vikulin I.M., Stafeeyev V.I. Physics of semicon-
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296 p.
2. Stafeeyev V.I. FGUP Scientific Production Ama-
lgamation. – M.: Orion, 2008. – 103 p.
3. Stafeeyev V.I. Influence of resistivity of the thic-
kness of semiconductor on shape of current-
voltage characteristics of diode//JTF. – 1958. –
№ 8. – P. 1631.
4. Mirsagatov Sh.A., Aytbayev B.U., Rubinov V.M.
//FTP. – 1996. – Vol. 30, №.3. – P. 550.
5. Ambrozyak. Design and technology of semicon-
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THE INJECTION PHOTO DIODE ON THE BASIS OF nSi-nCdS-n+CdS HETEROSTRUCTURES
ФІП ФИП PSE, 2013, т. 11, № 3, vol. 11, No. 3
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