The effect of the substrate temperature, during molecular beam epitaxial growth, upon the migration of Si atoms in δ-doped or planar-doped GaAs was investigated by using secondary ion mass spectrometry. The results for δ-doped GaAs revealed a measurable spread of Si, which increased by about 8nm when the substrate temperature was increased from 580 to 640C. For substrate temperatures below 580C, the measured width of the Si profile was limited by the resolution of the secondary ion mass spectrometer. Magnetotransport measurements were also performed in order to determine dopant spreading. The Si migration which was measured by means of secondary ion mass spectrometry was in qualitative agreement with the transport results. However, the secondary ion mass spectrometry data indicated larger Si areal densities. Two mechanisms, auto-compensation and electron localization by a DX center, were believed to be responsible for the latter observations.

Secondary-Ion Mass Spectrometry Study of the Migration of Si in Planar-Doped GaAs and Al0.25Ga0.75As. A.M.Lanzillotto, M.Santos, M.Shayegan: Applied Physics Letters, 1989, 55[14], 1445-7