The effect of Al upon deep-level defects in material which had been grown by molecular beam epitaxy was studied by using deep-level transient spectroscopy. Samples which contained 0.1 or 1%Al were studied. At least 9 different deep levels were detected, and their emission rate signatures, capture cross-sections, concentrations, and junction depth profiles were determined. These deep levels were compared with the M levels that were normally found in molecular beam epitaxial n-type material. The emission rates of the deep levels were found to shift to higher values with decreasing Al concentration. This was attributed to lattice strain and to random alloy effects. The relative concentrations of deep levels underwent large changes as the Al concentration was increased from 0.1 to 1%. Doping with up to 0.1%Al did not seem to reduce the deep level concentration; unlike other isovalent dopants such as In and Sb. A further increase in the Al concentration to 1% was found to lead to a marked increase in the overall deep-level concentration.

U.S.Qurashi, M.Z.Iqbal, N.Baber, T.G.Andersson: Journal of Applied Physics, 1995, 78[8], 5035-41