SURFACE DEFECT FORMATION IN GAAS-LAYERS GROWN ON INTENTIONALLY CONTAMINATED SUBSTRATE BY MOLECULAR-BEAM EPITAXY

The origin of oval defects of GaAs layers grown by molecular beam epitaxy (MBE) has been studied using intentionally contaminated GaAs substrates. Diamond and Al//2O//3 particles, and Ga and In droplets are used as contaminants. The surface defect shape caused by the particles is very similar to that of oval defects in our MBE grown layers which have a pit in the middle. This is strong evidence that one of the origins of the oval defects is a nonreactive and nonvolatile small particle. The shape of surface defects due to Ga or In droplets is different from that due to diamond or Al//2O//3 particles in that the former do not have a pit. Oval defects with a pit in MBE grown layers cannot be ascribed to the group III droplets spit out from effusion cells.