Androsiuk M. Improvement of technology of cultivation of semi-insulating GaAs bulks of large diameter

Dissertation is devoted to improvement of cultivation technology of semi-insulating GaAs ingots of large diameter. It was determined that when GaAs has a diameter of 100 mm, the maximum values of the dislocation density achieve 2,3*10^5 сm^(-2) and have insular character. The methods of calculation of thermal stress fields for crystal growth in the direction of (100) are improved; according to these methods the design of thermal unit is developed. Such methods allow to grow single crystalline bulk of semi-insulating GaAs, doped with Cr, with dislocation density 1,15-2,3*10^5 сm^(-2) . The methods of determining the optical homogeneity of semi-insulating GaAs with different electrical properties are worked out. According to proposed method the studying of optical characteristics of GaAs wafer with (100) orientation and a diameter of 100 mm is conducted. The research showed the presence of optical anomalies in the form of local islands in the plane of the wafer. The dislocation structure of single crystalline bulk of GaAs (diameter 100 mm) grown by Czochralski method is experimentally investigated, and it is found that high-temperature annealing results in a reduction of the dislocation density in the 1.2-1.3 times.