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Description A modified technique for the growth of Ge-rich Ge-Si single crystals is developed on the basis of the vertical Bridgman method using a Ge seed and a Si source rod. Single crystals were grown in two stages (Fig.1.). In the first stage, a Si source rod was partially immersed in the Ge melt above the seed. A gradual increase in the Si content in the melt leads to constitutional supercooling at the crystallization front and to the growth of an inhomogeneous Ge-Si buffer single crystal. The first stage ends when the temperature at the crystallization front becomes equal to the liquid’s temperature of the specified composition of the Ge-Si system. In the second stage, a homogeneous Ge-Si single crystal is grown while maintaining a constant growth temperature. The growth temperature is controlled by an appropriate balance between the pulling and feeding rates. Relations determining the optimal process parameters (the pulling and feeding rates and the temperature gradient at the crystallization front) for growing crystals of specified composition are obtained. Innovative Aspects and Main Advantages Growth of Ge-Si single crystals with desired graded and uniform compositions without using adequate solid solutions seed rods. Areas of Application The potential application include optoelectronic devices, thermoelectric power generation, intrinsic and extrinsic photo detectors, solar cells, substrate for epitaxial growth techniques. Stage of Development Laboratory tested technology for preparation of uniform Ge- Si single crystals with silicon content up to 15 %. 32 Science Opportunities in Azerbaijan Growth of Uniform Ge-Si Solid Solution Single Crystals by the Modified Bridgman Method Using a Ge Seed Contact Details Institute of Physics Contact person: Azhdarov Gusnu Khalil Address: 33, H. Javid Avenue AZ1143, Baku, Azerbaijan Fig.1. Temperature distribution in the heater (left) and the schematic diagram of the growth of homogeneous GeSi single crystals (right): (A) starting point, (B) stage 1 (growth of a buffer crystal of variable composition on a Ge seed), and (C) stage 2 (growth of a homogeneous GeSi crystal on the buffer crystal) Fig.2. Calculated distributions of Si along the three Ge-Si ingots grown in two stages to obtain crystals with a Si content of 10, 20 and 30 at.% in the homogeneous part. The calculations assumed that the melt height at the starting point is 100 mm and the temperature gradient in the growth zone of the buffer crystal is 50K/cm. Tel: (+994 12) 438 4503 E-mail: zangi@physics.ab.az
Technology Profile Creation of γ -Detectors on CuGaSe 2- Based Sensitive Materials Description CuGaSe2 semiconductive compound have been grown by gas transport reaction method. Crystalline iodine is used as a transporter. Obtained single crystals are p-type conductivity, resistivity is ρ=102÷103 Ohm*cm at 300 K. Obtained single crystals take the form of trihedral prisms with the most developed mirror plane (1 2). To carry the experiments single crystals have been ground by the dusts N30, N10, N7, then glazed with diamond pastas. To refine the surface, the samples have been dipped in ethanol. Then the contacts of In-Ga eutectic were plotted on samples. Distance between the contacts is 1мм. Dependence of resistivity with γ-radiation doze have been also investigated. Samples have been radiated by Co60 isotopes in MPX-Y-25. Innovative Aspects and Main Advantages Preliminary investigations show that the working range of CuGaSe 2 is 35-102 R/s. Specific resistance has been changed by four orders in this range (economically sound). Areas of Application γ -detectors for industrial spectroscopy. Stage of Development Creation of γ–detectors with small threshold sensitivity: development stage, laboratory tested. Contact Details Institute of Physics Contact person: Kerimova Tahira Gazi kizi Address: 33, H. Javid Avenue AZ1143, Baku, Azerbaijan Tel/Fax: (994 12) 432 4336 E-mail: ktaira@physics.ab.az 33
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Page 53 and 54: Technology Profile Ethyl Ether of 2
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