TEMPERATURE-DEPENDENCE OF THE FERMI-LEVEL IN LOW-TEMPERATURE-GROWN GAAS

A variable-temperature reflectance difference spectroscopy study of Ga As grown by molecular beam epitaxy at low-temperature GaAs (LT-GaAs) s hows that the Fermi level is mostly determined by the point defects in samples annealed at below 600 degrees C and can be shifted by photoqu enching the defects. The Fermi level is otherwise almost temperature i ndependent, leading to an estimated width of the defect band of 150 me V in the as-grown sample, For LT-GaAs annealed at 850 degrees C, the F ermi level is firmly pinned, most Likely by the As precipitates. (C) 1 998 American Institute of Physics.