Electrical Properties of a Native Oxide on Gallium Phosphide

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A vitreous native oxide can be grown on by oxidation in a concentrated solution of hydrogen peroxide, and this oxide effectively passivates light‐emitting devices. This paper reports the first electrical characterization of this native oxide. Electrical measurements were performed on MOS structures prepared by growing a native oxide film 500–1000AÅ thick on the face of an n‐ or p‐type wafer and evaporating an Au field plate on the oxide. The refractive index of the oxide film was 1.58. Current‐voltage and capacitance‐voltage characteristics show that the native oxide is an electrical insulator, with a low frequency dielectric constant , and a dielectric breakdown strength of after annealing in nitrogen at 250°C. Current‐voltage behavior shows a linear dependence of In , typical of field‐enhanced thermionic emission. The characteristics are nonsymmetric with respect to field plate polarity, suggesting the conduction mechanism to be surface‐barrier‐controlled emission, with a barrier height , as determined from the temperature dependence of the characteristics. The dielectric constant determined from the slope of the characteristics by using a field‐enhanced thermionic emission model agrees with the value obtained from capacitance measurements. Capacitance‐voltage characteristics show accumulation and deep depletion behavior. Analysis of deep depletion curves yields a surface charge density for both p‐ and n‐type samples. Values of for the substrates obtained from deep depletion data are in good agreement with the values obtained from Hall measurements on the substrate material.