SURFACE DAMAGE ON GAAS ETCHED USING A MULTIPOLAR ELECTRON-CYCLOTRON-RESONANCE SOURCE

Surface damage on GaAs induced by etching using an electron cyclotron resonance (ECR) source has been studied as a function of pressure, microwave power, sample distance from the ECR source, RF power, and gas composition. Damage was evaluated by measuring the current-voltage (I-V) and capacitance-voltage (C- V) characteristics on Schottky diodes fabricated on the etched surface. Etch-induced damage is found to depend mainly on the ion energy and the concentration of reactive species. The diode characteristics are improved when the samples are etched at lower pressure, higher microwave power, and closer distance to the ECR source. The diodes become more leaky and the intercept voltage extracted from the C-V measurements increased at higher RF power, which suggests the formation of a heavily damaged layer at higher ion energy. It is also found that an Ar plasma introduces more damage than a N2 plasma as observed by a higher ideality factor and a lower barrier height on the samples etched by Ar sputtering. Addition of Cl2, as little as 10%, results in diode characteristics close to that of the unetched sample. The damage observed can be classified into major and minor degrees of damage. In this study, most of the samples have only minor damage. Major damage was observed only on samples that were etchecl at high RF power or with a low concentration of reactive species.