IDEA #1CW1E1 GROWTH OF UNIFORM Ge-Si SOLID SOLUTION SINGLE CRYSTALS BY THE MODIFIED BRIDGMAN METHOD USING A Ge SEED

GROWTH OF UNIFORM GE-SI SOLID SOLUTION SINGLE CRYSTALS BY THE MODIFIED BRIDGMAN METHOD USING A GE SEED 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 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. temperature of liquidus the the 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 The technology for preparation of uniform Ge-Si single crystals with silicon content up to 15 % has been developed. Laboratory tested. 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) i S % . t a , c C 30 20 10 0 0 20 40 60 80 100 l, mm 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. Contact Details Institute of Physics Contact person: Azhdarov Gusnu Khalil Address: 33, H. Javid Avenue AZ1143, Baku, Azerbaijan Tel: (+994 12) 438 4503 E-mail: zangi@physics.ab.az