Photoluminescence studies on over-passivations of (NH4)2Sx-treated GaAs

Abstract

Over‐passivation films of silicon nitride (SiN) and silicon dioxide (SiO₂) on (NH₄)₂S_x‐treated GaAs deposited by various kinds of systems were studied with photoluminescence measurements. Among the various kinds of systems commonly used in semiconductor device fabrication processes, electron cyclotron resonance chemical vapor deposition (ECR‐CVD) produces undamaged over‐passivation films and it appears to be a promising system. The silicon nitride and silicon dioxide deposited at room temperature by ECR‐CVD have the same PL intensity. For SiN, the effect of the treatment is enhanced by annealing while a gradual degradation with increasing temperature is observed for SiO₂. By using ECR‐CVD SiN for sulfur‐treated GaAs passivation, the luminescences of free excitons and donor bound excitons are observed even for bulk‐grown GaAs at 4.2 K, which indicates the reduction of the recombination centers at the surface.