Effect of near-contact regions on the interpretation of ohmic behavior in trap-dominated relaxation semiconductors

The influence of near-contact electrical field nonuniformities on the injection of minority carriers into semi-insulating GaAs has been investigated experimentally. Variable length p+-v-n+ (200–10 μm) diodes are used to show that near-contact regions do affect the electrical measurements in high-resistivity trap-dominated semiconductors even though linear I-V characteristics are observed. As the diode length is decreased from 200 to 10 μm, the current density through the device, at a constant average field, decreases by a factor of 10. The experimental results are compared, with good agreement, to a previously proposed theoretical model in which semi-insulating GaAs is treated as a trap-dominated relaxation semiconductor.