Systematic temperature-dependent capacitance-voltage and conductance measurements were used to study the electrical characteristics of molecular beam epitaxy (MBE) and atomic layer deposition (ALD) oxides on In0.2Ga0.8As/GaAs. The distribution of interfacial density of states (D-it) within the band gap of In0.2Ga0.8As was deduced with the conductance method. The MBE-grown Ga2O3(Gd2O3)/In0.2Ga0.8As, with an excellent tailored interface, has given D-it values of similar to 5 X 10(11) eV(-1) cm(-2) above, similar to 2 x 10(12) eV(-1) cm(-2) below, and 1-7 X 10(12) eV(-1) cm(-2) around the mid-gap region (0.5-0.7 eV above valence band maximum (E-V)); the high D-it value near the mid-gap, extracted at 100 and 150 degrees C. may be related to the temperature effect, which tends to induce more trap excitations. In contrast, the ALD-Al2O3/In0.2Ga0.8As has yielded higher D-it values of > 10(13) eV(-1) cm(-2) around the mid-gap region. (C) 2011 Elsevier B.V. All rights reserved.