AVS2001 Session PH-ThP: Poster Session

Thursday, November 1, 2001 5:30 PM in Room 134/135
Thursday Afternoon

Time Period ThP Sessions | Topic PH Sessions | Time Periods | Topics | AVS2001 Schedule

PH-ThP-1 Photoconductivity Perculiarities of γ- Irradiated Silicon, Doped with Sulfur in Spectral Region 10,6 MCM
A.V Karimov, R.Sh. Avezov (Academy of Sciences of Republic Uzbekistan); V.T. Tulanov (National University of Uzbekistan named after M.Uilugbek, Uzbekistan)
γ-irradiation influence on Si < s > photoconductivity in spectral region 10,6 mcm was investigated. It was found that while compensation degree was increased both dark and light resistivities increased by 3-4 orders. Photoconductivity of sulfur doped silicon in the region of 10,6 mcm was investigated very poor. We know only one work,1 fulfilled under photoreciever cooling up to 5 K. The purpose of this paper is to investigate γ-irradiation influence on Si photoconductivity under cooling up to liquid nitrogen temperature. It is known that under γ -irradiation of silicon a number of donor and acceptor levels are created in the gap.2 As donor levels are placed in the lower half of the gap and sulfur creates a number of donor levels in the upper part of the gap, they don’t reveal themselves in 10,6 mcm photoconductivity. Only acceptor levels have influence, decreasing the filling of donor levels created by sulfur and free electrons concentration in conductivity band. The samples were investigated with specific resistivity 80 Ω.cm., produced by sulfur diffusion into crucileless p-type silicon with initial specific resistance 1600 Ω.cm. Samples were of parallelogram form with dimensions 10 x 8 x 1 mm3. Two nickel contacts were drifted electrochemically on one side of greater area at 7mm apart from one another. As irradiation source there was used impulsive CO2 laser LGI-50, that gives impulse of 150 mcs duration and 13 mJ energy. Direct voltage 10 V was applied to the sample. Dark current value and photoresponse were measured by memorizing oscillograph S8-12. As γ-irradiation source there was used 60Co, that created flux 1,7·1012 quanta/cm2·s. Kinetic equation for one level model (but with several values of energetic levels) was solved and it was established that no less than two energetic levels in semiconductor’s gap take part in 10,6 mcm photoconductivity.


1 N. Sclar. Infrared Physics. 1976, V.16, P.435
2 V.C. Vavilov, I.P. Kekelidze and L.S. Smirnov. Influence of radiations on the semiconductors. M. Nauka, 1988.
PH-ThP-2 Using the Ultrasound Treatment for Grain Boundary Passivation and Improvement of Multi-Si Recombination Properties
A.V Karimov, Kh. Ismailov, Sh.N. Bahronov (Academy of Sciences of Republic Uzbekistan)
The photoconverters (PC) has been produced on the base of n and p type multicrystalline silicon with the thickness of 250-300 µm. The technological route of PC included the chemical and mechanical treatments of the wafers (cutting, chemical and mechanical polishing, chemical cleaning and drying), p-n junction was formed by boron thermal diffusion (T~1000-1070 °C) or phosphorous (T~930-970 °C) those penetrated to 0.4-0.7 µm from the solid state reused target. The multi-layer system Ti-Ni-Cu has been used as a collector. The annealing of contacts was carried out at T~ 540-600 °C. The contact frontal topology has been chosen as one- and two-sided grid with the collector buss width of 1mm and contact grid - 0.2 mm. The distance between strips was 3mm. The silicon monoxide (d~ 1000 A) and dioxide SnO2 layers were formed by CVD method. This layers were used as antireflection coatings. The total PC area was ~2 cm2. The samples have been used to study the influence of ultrasonic treatment. The samples have been put into bath with ethanol. On the bottom of the bath was placed the ultrasonic wave sensor (CTS-19). Generator G3-41 with controllable output power exited it. For our case 2.5 MHz frequency and 1 W/cm2 power were used. The exposure time was chosen experimentally, all measurement was carried out at room temperature. Study of the spectral characteristic of solar cells based on multicrystalline Si under the ultrasonic treatment shown the significant dependence on the exposure time. For example, the 40 minutes exposure leads to photosensitivity increasing. The following increasing of the exposure time up to 120 minutes caused reducing of the photosensitivity on 10-15 %. The spectral characteristics in short-wave spectral range are changed substantially compared to long-wave range. The voltage-current characteristics behave analogously, but they demonstrate the increasing of open circuit voltage (~5%). The dependence of short circuit current on the exposure time in the USW is qualitative agreed with the photocurrent spectral dependence. Totally the changing of the solar cell parameters can be connected with series resistance, and with changing of the material parameters.
Time Period ThP Sessions | Topic PH Sessions | Time Periods | Topics | AVS2001 Schedule