Low interfacial density of states around midgap in MBE-Ga2O3(Gd2O3)/In0.2Ga0.8As

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 (Dit) 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 Dit values of ∼5×1011 eV−1 cm−2 above, ∼2×1012 eV−1 cm−2 below, and 1-7×1012 eV−1 cm−2 around the mid-gap region (0.5-0.7 eV above valence band maximum (EV)); the high Dit value near the mid-gap, extracted at 100 and 150 °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 Dit values of>1013 eV−1 cm−2 around the mid-gap region.