Metal-Vanadium Pentoxide-Silicon Diodes with Highly Variable Capacitances

摘要

Large-area metal-metal oxide-semiconductor diodes (top contact diameter = 1.6 mm) have been fabricated by evaporating vanadium pentoxide, V2O5, on carefully prepared surfaces of 12-ohm-cm n-type silicon wafers, firing at 700C, evaporating nickel for contact to the oxide, and chemically depositing nickel on the sub-surface of the silicon wafer to achieve ohmic contact to the silicon. Reverse breakdown of the diodes was 80 volts or higher, varying with oxide thickness and care in surface preparation. Capacitance variation with frequency at zero bias was determined over the range 15 kHz - 5 MHz. The data showed a decrease in capacitance with frequency from 2.750 nF at 15 kHz to 0.250 nF at 5 MHz. Capacitance variations with bias for various frequencies over the range 100 kHz - 5 MHz were also determined. For the frequency range, 100 kHz - 2 MHz, capacitance increased with forward bias, attained a maximum value in the interval 0.3 to 1.5 volts above zero bias, and decreased thereafter with increased forward bias. Each peak capacitance value occurred at successively lower forward bias values as frequency increased. Capacitance ratios greater than 60:1 were obtained for the frequency range 100 kHz through 1 MHz with more than 60% of the change occurring within the interval 0.4 to 0.6 volts reverse bias. (Author)