Plasma anodic oxidation of semiinsulating GaAs

A technique is presented for the plasma anodic oxidation of semiinsulating (SI) GaAs surfaces at elevated sample temperatures (up to 230°C) the anodization current being fed vertically across the semiconductor. Capacitance and resistance measurements were performed on corresponding MOS structures for the determination of the lowest temperature at which the oxide growth can proceed. The oxide/SI-GaAs interface properties were investigated by correlation of DLTS, photoluminescence and X-ray reflectivity methods with the aim to better clarify the oxidation kinetics. Moreover, it was determined that the interface region seems to be better formed, being thinner, when a thin aluminium coverage layer is deposited on the SI-GaAs surface before the oxidation process. On the basis of our experimental results, we presume that each anodic oxidation process can be characterized by a cross section of the reaction of the oxygen ions with the semiconductor atoms due to the different oxidation state of the latter which is determined by given oxidation conditions. Its value for SI-GaAs sample at 230°C has been calculated to be ∼ 3.0 × 10−14cm2.