ISSN 10637397, Russian Microelectronics, 2012, Vol. 41, No. 3, pp. 169–171. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © B.A. Abdurakhmanov, Kh.M. Iliev, S.A. Tachilin, A.R. Toshev, 2012, published in Mikroelektronika, 2012, Vol. 41, No. 3, pp. 188–190.
The current technological methods of manufactur
ing and semiconductor materials which are used in the
design of efficient solar cells (SCs) with stable param
eters and energy conversion efficiency (ECE) have
almost reached their limit. To further improve the
basic parameters of solar cells, we must use fundamen
tally new semiconductor materials or new physical
A real way to improve the parameters of SCs is to
use a singlecrystal photovoltaic devices based on the
internal germaniumsilicon heterojunctions [1–8],
which provide great opportunities in the construction
of nanoheterosystems for the next generation of pho
tovoltaic devices. Methods for creating arrays of Ge
quantum dots distributed on an atomically clean Si
surface have been developed at the Institute of Semi
conductor Physics, Siberian Branch, Russian Acad
emy of Sciences for the Ge–Si system [6, 7]. We can
consider a unified dense array of nanoclusters in the
bulk semiconductor matrix by quantum transporta
tion of charge carriers in a single electronhole sub
system as a new class of semiconductors with an inter
mediate or detached allowed zone . Theoretical
estimates show that at low production costs, the effi
ciency of converting radiation to electricity for such
materials can reach 60%. Therefore, it becomes highly
relevant to investigate the possibility of the synthesis of
materials with clusters of Ge in the silicon matrix and
production of solar cells based on it.
The content of germanium atoms and their distri
bution in depth was investigated by Xray microprobe
analysis Jeol Super Probe JXA8800 RRL.
To investigate the parameters of SCs under the
same conditions simulator solar radiation, produced
by incandescent lamps with a correction filter, was
used. We used a spherical reflector and a condenser
consisting of two planoconvex lenses to obtain the
strictly parallel direction of the radiation.
A 1000 W lamp and quasiflat filament were used in
the simulator, which allowed us obtain a small nonuni
formity of the density of the radiation flux on the surface
of the test SCs. The correction lamp’s spectrum to the
solar AM 1.5 was performed using a special liquid filter.
We used a KEF mark singlecrystal silicon grown
by the Czochralski process with a resistivity of 0.5 to
cm with an oxygen concentration of
Diffusion of germanium was performed by a specially
developed lowtemperature diffusion technology .
SCs were fabricated from the obtained material
with Si–SiGe–Si microheterojunctions.
tions were formed by diffusion of boron with the use of
boron nitride plates. The depth of the
m. Current collection contacts were created by ther
mal evaporation of nickel through the mask in a vacuum,
which were tinned by dipping into POSC5018 mark
layer thickness of
Å was used as an
antireflective coating. Photocells were fabricated in
the form of parallelepipeds with dimensions of 1.5 cm
cm and a thickness of 380
RESULTS AND DISCUSSION
The distribution of germanium atoms in the surface
region of the obtained samples is shown in Fig. 1. It is
seen that the surface content of germanium atoms is
more than the silicon ones for a depth of up to 1
i.e., it is a gradedgap structure on the basis of a con
solid solution with
> 0.5; then, the
content of germanium atoms is dramatically reduced,
and it is reduced to such an extent at
m that it
becomes difficult to determine the content due to the
limited sensitivity of the instrument.
Silicon Solar Cells with Si–Ge Microheterojunctions
B. A. Abdurakhmanov, Kh. M. Iliev, S. A. Tachilin, and A. R. Toshev
Tashkent State Technical University, Universitetskaya st., 2, Tashkent, 700095 Uzbekistan
Received August 30, 2011
—It was found that annealing germaniumdoped singlecrystal silicon at
leads to the forma
tion of internal Si–SiGe–Si microheterojunctions, which increase at an efficiency of 2.5% of solar cells fab
ricated on its basis.