Effect of thermal annealing conditions on the microdefect formation in undoped GaAs single crystals grown by Czochralski method

The effect of thermal annealing conditions on the microdefect formation in undoped GaAs single crystals grown by the Czochralski method has been studied by X-ray diffraction and metallographic analyses. It is found that the standard heat treatments performed with the aim to relieve elastic stresses and to increase the homogeneity of wafers substantially affect microdefects formed in the crystal. Upon annealing, the micro-defects in ingots and wafers exhibit different behavior. Prolonged annealing leads to an increase in the sizes of large microdefects but does not suppress the formation of small-sized microdefects. The latter defects are formed at T< 950°C upon cooling from the annealing temperature, and their number strongly depends on the density of dislocations, which serve as sinks for intrinsic point defects.