Si diffusion and segregation in low-temperature grown GaAs

Heavily Si-doped (5 X 10” cmm3) low-temperature GaAs (LT-GaAs) sandwiched between undoped LT-GaAs layers has been grown by molecular beam epitaxy and annealed to 900 “C. Transmission electron microscopy showed that within the first few minutes of annealing an accumulation of As precipitates formed near each Si-doped/undoped LT-GaAs interface. With further annealing Si segregation to As precipitates was detected with secondary ion mass spectroscopy in the form of deltalike peaks at the As precipitate accumulations. The Si diffusion coefficient was initially concentration independent at a value of 2.5 X lol3 cm2/s, comparable to diffusion under intrinsic conditions in As-rich GaAs grown at normal temperatures. After a 60 min anneal the Si concentration in the As precipitates reached 2.5 x 102’ cmm3.