Photoconverters with microrelief p-n-junction on a basis of p AlxGa₁₋x-p GaAs-n GaAs-n⁺ GaAs heterojunction
Given in this work are the results of studying the process of creation of diffusion and epitaxial layers in microrelief structures. It has been shown that photoconverting structures with a microrelief interface were different in their efficiency under the used level of the illumination intensity.
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2005
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| Zitieren: | Photoconverters with microrelief p-n-junction on a basis of p AlxGa₁₋x-p GaAs-n GaAs-n⁺ GaAs heterojunction / A.V. Karimov, D.M. Yodgorova // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2005. — Т. 8, № 1. — С. 79-82. — Бібліогр.: 5 назв. — англ. |
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| author | Karimov, A.V. Yodgorova, D.M. |
| author_facet | Karimov, A.V. Yodgorova, D.M. |
| citation_txt | Photoconverters with microrelief p-n-junction on a basis of p AlxGa₁₋x-p GaAs-n GaAs-n⁺ GaAs heterojunction / A.V. Karimov, D.M. Yodgorova // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2005. — Т. 8, № 1. — С. 79-82. — Бібліогр.: 5 назв. — англ. |
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| container_title | Semiconductor Physics Quantum Electronics & Optoelectronics |
| description | Given in this work are the results of studying the process of creation of diffusion and epitaxial layers in microrelief structures. It has been shown that photoconverting structures with a microrelief interface were different in their efficiency under the used level of the illumination intensity.
|
| first_indexed | 2025-12-07T17:48:42Z |
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Semiconductor Physics, Quantum Electronics & Optoelectronics, 2005. V. 8, N 1. P. 79-82.
© 2005, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
79
PACS: 84.60. Jt
Photoconverters with microrelief p-n junction on a basis of
p-AlxGa1-xAs – p-GaAs – n-GaAs – n+-GaAs heterojunction
A.V. Karimov, D.M. Yodgorova
Physical-and-Technical Institute of the Scientific Association "Physics-Sun" of the Academy of Sciences of the Republic
of Uzbekistan, 2b, Mavlanova Str., 700084 Tashkent
Phone: 998-71-1331271, fax 998-71-1354291
E-mail: karimov@physic.uzsci.net
Abstract. Given in this work are the results of studying the process of creation of diffusion
and epitaxial layers in microrelief structures. It has been shown that photoconverting
structures with a microrelief interface were different in their efficiency under the used level
of the illumination intensity.
Keywords: photoconverter, microrelief, p-n junction, buffer layer, epitaxy.
Manuscript received 14.12.04; accepted for publication 18.05.05.
1. Introduction
Various methods of surface treatment became used in
technology of producing the semiconductor structures
with antireflection coatings. In particular, anisotropic
etching that could decrease optical losses on the surface.
The most effective results were obtained on silicon
structures with depression in the form of “honeycombs”
and “pyramids”. They served as light traps that allow to
markedly increase the degree of solar element efficiency
as compared with the usual flat ones by 15 – 20 %.
It should be noted that microrelief interfaces could be
created inside the volume of semiconductors and in the
range of photocarrier separation. Photodetector with the
Shottky barrier formed on a surface of quasi-lattice type
or dendrite one exemplifies it. Here the p-n junction or
rather the junction of metal-semiconductor reproduces
the surface form. As a result, the structures with
microrelief surface turned out to be of high performance
as compared to structures with a flat surface.
Remark what would be if to create microrelief
structure in p-n junction. So preferred parts of p-n
junction should be increased as compared with the
metal-semiconductor ones. In this aspect, the structure
with p-n junction possesses high radiation hardness and
capacity to operate under concentrated radiation, etc.
Here it emerges one question more: what difference
would arise between structures with flat and microrelief
junctions.
Information about creation of structures with the
microrelief interface of p-n junction by using liquid-
phase epitaxy is absent in literature up to date. As for
obtaining a microrelief surface, it is known that the
technique of anisotropic etching enables to obtain the
surface of quasi-lattice, dendrite and bi-lattice types [1].
At first sight, growing them on a textured surface
appropriated thin layers could be obtained as homo- and
heterostructures with microrelief interface.
It may be conceived that the structure with a p-n
junction possessing a repeated surface microrelief has
been artificially crimped. By smoothing out this relief, it
would be obtained the same flat structure. However,
preliminary results of researching these microrelief
structures have shown that they enable to increase the
spanning angle of an optic signal as compared with the
flat structures. The heterostructure with a microrelief
interface of the p-n junction was not sufficiently studied,
and it is required to perform further researches.
In this work, given are the results of studying the
photoconverters with the microrelief p-n junction based
on p-AlхGa1–xAs – p-GaAs – n-GaAs – n+-GaAs
heterostructure. The research was carried out using the
structures with buffer layers and heterolayers.
2. Experimental results
2.1. Growing the buffer layers
The heterostructure of the following composition
p-AlхGa1–xAs – p-GaAs – n-GaAs could be prepared by
various methods [2, 3] as well as by the liquid-phase
epitaxy method. In certain cases, each layer n-GaAs and
p-AlхGa1–xAs is grown consecutively or after growing
heterolayer p-AlхGa1–xAs on the operation surface GaAs.
Besides, used is a special annealing for diffusion of an
acceptor impurity from solid solution into n-GaAs or
n+-GaAs [4]. To prepare p-AlхGa1–xAs – p-GaAs –
n-GaAs – n+-GaAs structure of a solar element, we used
the equipment for epitaxial growing gallium arsenide [5]
and its compounds. The used technological processes
provided the epitaxial growth of AlGaAs on the GaAs
substrate. It was confirmed by some methods of liquid
epitaxy. As a result, we came to the conclusion that the
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2005. V. 8, N 1. P. 79-82.
© 2005, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
80
Fig. 1. Cross cut of graphite cassette for epitaxy.
1 – basis, 2 – piston, 3 – substrate, 4 – solution-melt, 5 – stop,
6 – lid, 7 – window, 8 – capillary aperture.
Fig. 2. The surface of buffer layer obtained with piston
cassette.
process for growing the perfect layers needs to be
stopped sometimes or needs other methods ensuring
perfection of layers. To take it into account, we
developed a cassette with a piston (see Fig. 1).
Using this cassette, a deposition of GaAs buffer
layers on substrates was carried out from a limited
volume of solution-melt by forced cooling (without
isothermal liquid epitaxy). To support the growth of
high-quality epitaxial layers, we used the method of
GaAs liquid epitaxy by using an advanced technology.
The distinctive sign of this technology consists in that
base solution-melt from which the epitaxial layer was
grown on the descrete substrate was fed by discrete
portions. To realize the process, the system
(Ga+GaAs+х melt) was cooled for a selected time
interval Δt = t0 − t1. Then, the portion р1 separated from
common melt pn was fed to the substrate. This stage was
followed by the cooling the system for Δt = t1 − t2, and
then the next portion p2 was separated from solution-
melt and fed over p1, etc.
Temperature intervals ΔT and the volume of each
portion were chosen in the same way to create the next
temperature gradient ΔT for the process of growth to be
stopped. This way let to provide a permanent front of
crystallization, and so the growth of each microlayer
would be realized with a variable speed, namely, with
the decreased one. As a result, the concentration of
defects in each following layer would be decreased, and
increased perfection of structures could be obtained.
Chosing ΔT within the range 3 to 5 K under the initial
temperature of crystallization 815 – 830 ºC enabled to
obtain GaAs epitaxial layers starting from 4 – 8
monolayers to the thickness of 2 – 3 µm, Fig. 2.
After obtaining the buffer layers with satisfactory
parameters, we have a set of problems in realization of
the diffusion process and growth of epitaxial layers in
the same cassette and united process. With this aim,
we made a special combined graphite cassette for
diffusion and synchronous growth of epitaxial layers.
For the first time, we carried out series of diffusion
processes in the buffer layers and then, at the same
time, diffusion process and growth of p-AlGaAs
frontal layer were made.
2.2. Diffusion processes in the buffer layers
The diffusion process was carried in the developed
cassette with a quasi-closed volume and baffle between
the Zn resource and patterns. In the course of increasing
the temperature up to 800 ºC, the baffle was open and
the system was heat at this temperature for 70 –
90 minutes. All the process was carried out in epitaxy
conditions with hydrogen flowing through the reaction
chamber. Further cooling was carried out in the regime
of epitaxy.
The preliminary estimates of load characteristics
inherent to diffusion p-n junctions obtained using this
method on the buffer layers were carried out. It turned
out that increasing the Zn quantity from 90 to 190 mg
we observed increase of the open-circuit voltage from
0.4 to 0.6 eV. But in this case, we revealed a decrease of
the short-circuit photocurrent from 1700 down to
360 µA. The increase of the diffusion time up to 90 and
more minutes resulted in the increasing open-circuit
voltage. It could be explained by increasing the p-n
junction location depth. In spite of the fact that in the
latter case the duty coefficient was increased, however,
we got a positive effect.
These results show that it is necessary to find a
reasonable compromise between the diffusion time and
quantity of diffusing element.
2.3. Processes of diffusion and growth of p-AlGaAs
frontal layer
The processes of diffusion and following growth of
p-AlGaAs frontal layer were carried out by the way of
closing the baffle after reaching the required time of
diffusion (70-90 minutes) at the temperature of 800 ºC.
Thereafter, we increased the temperature up to 814 –
816 ºC to begin crystallization of the frontal layer and
provided the growth of p-AlGaAs layer by cooling the
system by 4-degree step with the following decrease in
the temperature of epitaxy.
Each process was realized simultaneously on two
n-GaAs buffer layers (one of them had a microrelief of
the dendrite type, while the other had a flat surface), and
both of them were subjected to Zn diffusion and
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2005. V. 8, N 1. P. 79-82.
© 2005, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
81
Parameters of photoconverter n+-GaAs – n-GaAs (buffer) – p-GaAs (diffusion layer) – p-AlGaAs (epitaxial layer)
structures
Parameters of photoconverter n+-GaAs – n- GaAs
(buffer) – p-GaAs (diffusion layer) – p-AlGaAs
(epitaxial layer) structures
Diffusion Zn,
acidification of p-
GaAs, T = 800 ºC,
mZn = 190 mg Flat Dendrite
N of
pattern
Regime of
growth of
buffer layer
n-GaAs
(1017 cm–3) t, min
Regime of
growth of
frontal layer
p-AlGaAs
(1019 cm−3) Ulum, V Ishc, µA Ulum, V Ishc, µA
0.1 0.12 0.7 6.0 23 T = 817 ºC
ΔT = 8
80 Т = 815 ºС
ΔТ = 4 S = 0.7 cm2 S = 0.49 cm2
0.38 0.8 0.6 5.0 24 Т = 825 ºС
ΔТ = 8
70 Т = 815 ºС
ΔТ = 4 S = 0.9 cm2 S = 0.81 cm2
25 Т = 824 ºС
ΔТ = 8
80 Т = 816 ºС
ΔТ = 5
0.6 5.0 0.6 8.0
26 Т = 825 ºС
ΔТ = 5
90 Т = 814 ºС
ΔТ = 4
0.4 5.0 0.4 7.0
following growth of p-AlGaAs. As a result, n+-GaAs –
n-GaAs (buffer) – p-GaAs (diffusion layer) – p-AlGaAs
(epitaxial layer) were prepared.
Morphology of the surface of heterolayers
(p-AlGaAs) arising on the quasi-lattice buffer n-GaAs
epitaxial layers has a tendency to be improved. So,
applying the shift method for growing from the melt
with an open surface, we could observe consecutive
improving of surface morphology.
If the surface of buffer layer to some extent repeats
asperity of substrate, then the surface of the heterolayer,
though its small thickness (1 – 2 µm), works to evening.
This tendency let to conclude that exact amount of Al
was responsible for positive changes in the process of
layer growth on the microrelief substrates.
The researches show that the layers of the solid
solution p-AlGaAs appeared to be more perfect as
compared with the above buffer layers. Comparing the
surface structure of buffer layers with that of the
heterolayer, we found that in heterolayer the quasi-lattice
is smoother, obviously due to sub-dilution of juts. Such
behavior of the heteroboundary could be explained by
the variable temperature of solid solution formation as
compared with that of the arsenide gallium crystal. As a
result, during the time of bringing the solution-melt
Al+Ga+GaAs+Zn in contact with the crystal GaAs and
reaching equilibrium between them, sub-dilution of the
solid phase take place. Therefore, the speed of growth in
deepenings is higher than that in juts. And finally, the
surface of the solid solution layer begins to become
smooth. The epitaxial layer p-AlGaAs is continuation of
diffusion p-GaAs and the obtained depth of the p-n
junction location (3 µm) is sufficient for the following
growth of the layer from the liquid phase without
prejudice to p-n junction. And also, the possibility to
preserve the microrelief boundary of the p-n junction
appears.
Summarized in Table are the parameters of obtained
photoconverter structures n+-GaAs – n-GaAs (buffer) –
p-GaAs (diffusion layer) – p-AlGaAs (epitaxial layer).
As can be seen from the table, as a ruler, the dendrite
samples show preferable performances, in particular,
under illumination (19200 lux) the open-circuit voltage
is equal to 0.5 – 0.7 V, the density of the short-circuit
current 6 – 12 mA/cm2.
Fig. 3. Load characteristics of heterostructures n+-GaAs – n-GaAs (buffer) – p-GaAs (diffusion layer) – p-AlGaAs (epitaxial
layer) with the flat p-n junction (a) and microrelief one (b).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2005. V. 8, N 1. P. 79-82.
© 2005, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
82
The initial parameters of flat and microrelief
structures at the room temperature and initial
illumination are practically identical. But with increasing
the illumination intensity, differences become clear.
So on the structures with the flat p-n junction and the
increased illumination intensity the load characteristics
becomes worse, but on the microrelief structures no
changes are observed (see Fig. 3b, illuminations 19200,
19500 and 20400 lux). In both cases, the short-circuit
current rises with increasing the illumination intensity
that may be caused an increase of the coefficient of
charge collection.
3. Conclusion
The obtained results show that diffusion processes
conducted for buffer layers by variable time give
practically relatives data on the parameters of
microrelief structures. It could be explained by the fact
that the epitaxial layer р-AlGaAs is a continuation of
diffusion р-GaAs, and the obtained location depth for
the p-n junction (3 µm) is sufficient to further growing
the layer from the liquid phase. The regimes of diffusion
chosen for photoconverter structures with the buffer
layers require a correction to be used in photoconverter
heterostructures obtained by synchronous realization of
the diffusion process and growth of the frontal layer –
p-AlGaAs.
References
1. Z. Jianhua, A. Wang, M.A. Green, F. Ferrazza,
19.8 % efficient “honeycomb” textured
multicrystalline and 24.4 % monocrystalline silicon
solar cells // Appl. Phys. Lett. 73 (14), p. 1991-1993
(1998).
2. P. Campbell, and M.A. Green, Light trapping
properties of pyramidally textured surfaces // J. Appl.
Phys. 62 (1) p. 243-249 (1987).
3. N.L. Dmitruk, О.Yu. Borkovskaya, R.V. Konakova,
et al., Influence of a scale-irradiation on the
characteristics of phototransformation of barrier
structures metal-arsenide of gallium with microrelief
by border undressed // Technical Physics Letters 72
(6), p. 44 (2002).
4. T.Ya. Gorbach, E.V. Pidpisniy, S.V. Svechnikov,
Morphology and optical properties of anisotropy
etching arsenide gallium // Optoelectronics and
Semiconductor Technique 13, p. 34-39 (1988).
5. A.L. Fahrenbruch, R.H. Bube, Fundamentals of solar
cells, photovoltaic solar energy conversion, New
York (1983).
|
| id | nasplib_isofts_kiev_ua-123456789-120643 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1560-8034 |
| language | English |
| last_indexed | 2025-12-07T17:48:42Z |
| publishDate | 2005 |
| publisher | Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| record_format | dspace |
| spelling | Karimov, A.V. Yodgorova, D.M. 2017-06-12T14:42:44Z 2017-06-12T14:42:44Z 2005 Photoconverters with microrelief p-n-junction on a basis of p AlxGa₁₋x-p GaAs-n GaAs-n⁺ GaAs heterojunction / A.V. Karimov, D.M. Yodgorova // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2005. — Т. 8, № 1. — С. 79-82. — Бібліогр.: 5 назв. — англ. 1560-8034 PACS: 84.60. Jt https://nasplib.isofts.kiev.ua/handle/123456789/120643 Given in this work are the results of studying the process of creation of diffusion and epitaxial layers in microrelief structures. It has been shown that photoconverting structures with a microrelief interface were different in their efficiency under the used level of the illumination intensity. en Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України Semiconductor Physics Quantum Electronics & Optoelectronics Photoconverters with microrelief p-n-junction on a basis of p AlxGa₁₋x-p GaAs-n GaAs-n⁺ GaAs heterojunction Article published earlier |
| spellingShingle | Photoconverters with microrelief p-n-junction on a basis of p AlxGa₁₋x-p GaAs-n GaAs-n⁺ GaAs heterojunction Karimov, A.V. Yodgorova, D.M. |
| title | Photoconverters with microrelief p-n-junction on a basis of p AlxGa₁₋x-p GaAs-n GaAs-n⁺ GaAs heterojunction |
| title_full | Photoconverters with microrelief p-n-junction on a basis of p AlxGa₁₋x-p GaAs-n GaAs-n⁺ GaAs heterojunction |
| title_fullStr | Photoconverters with microrelief p-n-junction on a basis of p AlxGa₁₋x-p GaAs-n GaAs-n⁺ GaAs heterojunction |
| title_full_unstemmed | Photoconverters with microrelief p-n-junction on a basis of p AlxGa₁₋x-p GaAs-n GaAs-n⁺ GaAs heterojunction |
| title_short | Photoconverters with microrelief p-n-junction on a basis of p AlxGa₁₋x-p GaAs-n GaAs-n⁺ GaAs heterojunction |
| title_sort | photoconverters with microrelief p-n-junction on a basis of p alxga₁₋x-p gaas-n gaas-n⁺ gaas heterojunction |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/120643 |
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