Abstract
In order to find the energy levels of the deep centers that cause a high resistance region at the interface between GaAs vapor epitaxial film and the substrate, three kinds of measurements were performed: i) time dependence of the capacitance of Schottky barriers, ii) temperature dependence of the reverse current of Schottky barriers, iii) photoconductivity of the high resistance region. From the variation in the time dependence of the capacitance measured at various temperatures, an activation energy for electrons at deep traps was found to be about 0.89 eV. When the depletion layer contained a high resistance region, the reverse current of the Schottky barrier was larger than the normal reverse current by about three orders of magnitude. The measured results on the temperature dependence of reverse current and on the photoconductivity spectrum of the high resistance region suggest the presence of three deep energy levels that range from about 0.3 eV to 0.6 eV above the valence band. Extrinsic negative photoconductivity was observed in the high resistance region.