A study was made of the role that was played by the wafer surface in the transient diffusion of Be. Samples were doped during molecular beam epitaxial growth, and were annealed (900C, 0.25 or 2h) under 2 different caps. In some of the annealed samples, the dopant was initially located near to the surface. In other samples, the dopant was initially located in a buried layer. Both types of sample were analyzed by means of secondary ion mass spectrometry. It was found that variations in the diffusion behavior under the various experimental conditions could all be qualitatively explained in terms of a model which took account of 3 important effects. These were the transient evolution of point defect populations, the injection of Ga vacancies by an oxide cap, and the efficiency of the surface in restoring point-defect equilibrium.

Effect of Encapsulant Material on the Diffusion of Beryllium in Molecular Beam Epitaxy Gallium Arsenide. Y.M.Haddara, M.D.Deal, J.C.Bravman: Applied Physics Letters, 1996, 68[14], 1939-41