Microscale Defect Kinetics in Melt-Grown GaAs.

Abstract : Our research on the kinetics of defects in melt-grown GaAs involved crystal growth experiments and post-growth treatments of crystals combined with extensive characterization of electronic properties related to defects. In our crystal growth experiments we used an especially constructed Czochralski-type puller equipped with a vertical magnetic field for the growth of GaAs under conditions of suppressed convection. We have identified for the first time a beneficial effect of the magnetic field for the compensation ratio and electron mobility (Ref. 1). Experiments on doping with oxygen of GaAs crystals grown by the Horizontal Bridgman technique have revealed an anomalous silicon segregation behavior governed by chemical reactions in a closed growth ampul rather than standard impurity distribution during the solidification (Refs. 2 and 3). Experiments on fast growth of GaAs by the LEC technique using pulling rates of up to 2 inch/h showed a significant decrease of EL2 concentration with increasing the pulling rate. We have shown that this effect originates from fast cooling of the crystal grown under high pulling rates (Ref.4). We have essentially completed a detailed study on the effects of plastic deformation on deep levels in GaAs (Refs. 5,6). This study combined electrical and optical characterization of crystals subjected to plastic deformation at 400 C.