Photo-reflectance methods were used to study the Fermi levels of annealed low-temperature material in structures which consisted of low-temperature GaAs on top of Si δ-doped GaAs. The diffusion of As precipitates across the interface between low-temperature GaAs and normal GaAs was observed by means of cross-sectional imaging using transmission electron microscopy. The Fermi-level pinning in low-temperature material was calculated by including a carrier-concentration correction which was due to the accumulation of As precipitates. The Fermi level was found to decrease from 0.7 to 0.5eV below the conduction band when the annealing temperature was increased from 600 to 900C.

W.C.Lee, T.M.Hsu, S.C.Wang, M.N.Chang, J.I.Chyi: Journal of Applied Physics, 1998, 83[1], 486-90