Control of Be diffusion in molecular beam epitaxy GaAs

Abstract

After molecular beam epitaxy GaAs is grown at 585 °C, substantial diffusion of Be occurs during growth of subsequent layers or during subsequent in situ annealing at 700 °C. By using an order of magnitude larger As4 flux than commonly used during growth and annealing, we were able to lower the Be diffusion coefficient by an order of magnitude. We also show that the Be diffusion coefficient is strongly dependent on the Be concentration. Different specimens were prepared with varying Be doping density, As4:Ga beam flux ratio, and annealing temperature. In these experiments, the Be concentration profiles were measured by secondary ion mass spectrometry and from them Be diffusion coefficients were calculated.