The effect of the substrate temperature, during molecular beam epitaxial growth, upon the migration of Si atoms in δ-doped or planar-doped Ga0.75Al0.25As was investigated by using secondary ion mass spectrometry. For substrate temperatures of 580 to 640C, the Si spread over about 35nm in δ-doped Ga0.75Al0.25As. For substrate temperatures below 580C, the measured width of the Si profile was limited by the resolution of the secondary ion mass spectrometer. Magneto-transport 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