Dopant diffusion was investigated via depth-profiling using secondary ion mass spectrometry of heterostructures which contained Be-doped short-period AlxGa1-xAs superlattices, where x ranged from 0.3 to 0.8, that had been grown by means of molecular beam epitaxy. Out-diffusion of Be into the undoped GaAs layers was observed only at a substrate temperature of 660C, when the Be concentration was 2 x 1018/cm3. At a dopant concentration of 2 x 1019/cm3, a marked increase in diffusion occurred at all growth temperatures. The solubility limits of Be were 1019/cm3 at x = 0.6, and 2 x 1018/cm3 at x = 0.8. Secondary ion mass spectrometry profiles revealed that the amount of diffused Be in the active region was twice as high in samples with a thin (450 to 600nm) p-type cladding layer.

Beryllium Diffusion in Short-Period AlxGa1−xAs/AlAs-Superlattices and Vertically Compact Laser Structures Grown by Molecular Beam Epitaxy. A.Gaymann, M.Maier, W.Bronner, N.Grün, K.Köhler: Materials Science and Engineering B, 1997, 44[1-3], 12-5