Distinguishing between EL2 and dislocation formation mechanisms in GaAs by mapping topographies

Abstract

Several models have been reported to investigate the relationships between the optically active defect level, EL2, and dislocation formation mechanisms. For undoped LEC grown GaAs, the comparison between EL2 and dislocation has been made using mapping capabilities. In this presentation, we aim to distinguish the formation mechanisms using three different types of mapping topographies on a broad base of materials including undoped and Si doped GaAs wafers grown by LEC and HB/GF techniques. The mapping topography methods used are photo-chemically etched growth striation, near infrared transmittance determined EL2, and molten KOH etched dislocation pits. Comparisons of different topographies are made on the same wafer in all cases. In brief, the EL2 distribution has shown good correlation with growht striation where EL2/growth striation have had only moderate to no correlation with dislocation distribution for undoped and Si doped GaAs regardless of growth techniques. The results suggest strongly that the formation mechanism for EL2 relates directly to solidification. The results also indicate that EL2 as a defect complex is only secondary in degree of importance in formation. The point defects and plastic deformation, when present, are dominant.