The passivation of interface states remains an important problem for III-V based semiconductor devices. The role of the most stable bound native oxides GaOx (0.5 ≤ x ≤ 1.5) is of particular interest. Using monochromatic x-ray photoelectron spectroscopy in conjunction with controlled GaAs(100) and InGaAs(100) surfaces, a stable suboxide (Ga2O) bond is detected at the interface but does not appear to be detrimental to device characteristics. In contrast, the removal of the Ga 3+ oxidation state (Ga2O3) is shown to result in the reduction of frequency dispersion in capacitors and greatly improved performance in III-V based devices.