GaAs結晶不純物偏析に対する磁場印加効果 : II. LEC GaAgにおける偏析現象

抄録

Effects of magnetic field on impurities and native defects distributions were investigated in detail in conjunction with the strengths of applied magnetic field. It was found that inhomogeneities of local impurity distribution caused by irregular striations and periodic striations were remarkably suppressed in the presence of magnetic field about 3000 Gauss during growth. It was confirmed that effective segregation coefficients of carbon and indium in GaAs approach unity as the magnetic field increases. Although the midgap deep donor EL2 concentrations only varied from 1 to 4 X 10^<16>cm^<-3> in the conventional LEC GaAs crystals, they ranged from far below 1 X 10^<15>cm^<-3> in Ga-rich melt to 1 X 10^<17>cm^<-3> in As-rich melt for the magnetic field applied LEC ( MLEC ) GaAs crystals. Segregation phenomena of EL2 were found to vary with the arsenic mol fraction in the melt in MLEC crystals. The homogeneity of the native defect and impurity distributions in MLEC crystals was far superior to that of LEC crystals, which resulted in homogeneous semi-insulating property of MLEC GaAs crystals. Based on these results, we have proposed a programmed magnetic field applied LEC crystal growth technique and demonstrated the controllability of the impurity distribution along the growth axis by this technique.