It was found that layers which had been grown by means of molecular beam epitaxy at low temperatures exhibited several interesting features. Concentrations of up to 2 x 1020/cm3 of neutral defects and up to 5 x 1018/cm3 of positively charged AsGa defects were found in as-grown layers. Nevertheless, the mobility of photo-excited electrons was as high as 20000cm2/Vs at about 130K. In view of the very high concentration of ionized defects, it was concluded that the best explanation of such a high mobility was that the AsGa defects interacted with ionized acceptors, A-. This led to the creation of AsGa+-A- dipoles, which did not scatter electrons as efficiently as did single ions. Numerical calculations of AsGa/acceptor interactions showed that dipole formation was possible in the present material and could lead to the observed increase in mobility.

K.P.Korona, M.Kaminska, J.M.Baranowski: Materials Science Forum, 1995, 196-201, 1773-8