Capacitance-voltage measurements on Schottky diodes with poor ohmic contacts

The frequency-dependent admittance of Al-GaAs Schottky diodes with nonideal ohmic contacts is tested, using a simple three-component small-signal equivalent circuit model. Both the ohmic and the rectifying contacts of this diode are produced during one process step. This simplifies the formation procedure and saves testing time and costs. However, the nonalloyed ohmic contacts lead to a high series resistance, minority carrier injection, and deep level influence. All of these effects give a frequency-dependent diode admittance. Frequency-dependent admittance analysis in a certain frequency range using the three-component equivalent circuit model leads to the space-charge capacitance of the diode reflecting only the free majority carriers. The method is highly suitable for the automatic routine control of semiconductor material properties, diode, or gate capacitances