Capacitance-voltage characteristics of Al-plasma anodic Al ₂O₃-GaAs diodes

Metal-insulator-semiconductor diodes were fabricated on an n-type GaAs substrate by means of plasma anodic oxidation of aluminum film evaporated on the GaAs substrate. The capacitance-voltage (C-V) characteristics of these diodes were significantly affected by the deposition rate of the aluminum onto the GaAs substrate. Depth profiles revealed by Auger electron spectroscopy show that the amount of gallium atoms migrated from the GaAs surface through the aluminum oxide film increases with decreasing the deposition rate of the aluminum. At the appropriate deposition rate, the C-V curves show the increase of capacitance in negative-bias (polarity of inversion) region at low frequency.