Electronic properties of Se-treated SiO2/GaAs interfaces

GaAs metal-insulator-semiconductor diodes with a Se-treated interface and photochemical-vapor-deposited SiO2 are investigated. The diodes show little frequency dispersion in the capacitance at any accumulation bias, only a few percent between 1 kHz and 1 MHz. Analysis using Terman’s method shows that the density of interface states near the midgap is drastically reduced. In addition, insertion of a Se-treated AlGaAs thin layer at the insulator/semiconductor interface is found to reduce the number of interface states near the conduction band minimum. These improved characteristics are preserved after annealing to 400 °C.