Voltage and Frequency Dependence of Differential Capacitance in Relaxed In0.2Ga0.8As/GaAs Schottky Diodes

Capacitance dispersion over frequency is investigated for relaxed In0.2Ga0.8As/GaAs Schottky diodes. While the high-frequency capacitance is voltage-independent, the low-frequency capacitance is seen to decrease with reverse voltage. Based on a Schottky barrier combined with a high-resistance layer containing traps, a simplified equation for the differential capacitance is derived to explain the capacitance-voltage-frequency relation. It is found that the high-frequency capacitance corresponds to the total thickness of the Schottky depletion and the high-resistance layer, while the low-frequency capacitance at a small reverse voltage is the Schottky depletion capacitance and at a large reverse voltage is the high-frequency capacitance.