Cathodoluminescence investigation of diffusion studies on the arsenic sublattice in gallium arsenide

While the diffusion mechanism on the Ga sublattice of GaAs is fairly well understood, the diffusion on the As sublattice is still under discussion. In this contribution the use of spectrally resolved and imaging cathodoluminescence (CL) for investigating diffusion phenomena is reported. Interdiffusion experiments with GaAsP/GaAs and GaAsSb/GaAs superlattice samples and in-diffusion experiments of phosphorus and antimony in GaAs were performed at various temperatures and arsenic pressures. The interdiffusion coefficient could be deduced from the energy shift of the superlattice luminescence bands. A comparison with conventional SIMS investigation of the superlattices shows that spectral CL is a simple and reliable alternative to SIMS for the investigation of interdiffusion in luminescing superlattices. Imaging CL studies of P in-diffusion in GaAs show that a high phosphorus partial pressure during diffusion causes the formation of a GaAsP phase, leading to a high density of dislocations which disturb the in-diffusion process. The formation of dislocations may be prevented by using a phosphorus partial pressure below 0.08 bar and an arsenic partial pressure above 0.1 bar. The As partial pressure dependence of the obtained diffusivities combined with results from other diffusion studies clearly demonstrate that P and Sb diffusion as well as arsenic self-diffusion on the As sublattice of GaAs is dominated by As self-interstitials.