Voltage Dependence of the Optical Response of a Pseudomorphic HFET-Photodetector

A pseudomorphic HFET has been used as a photodetector. The optical response of such a device was measured in the frequency range from 100 kHz up to 10 GHz. The response of the HFET-photodetector showed a strong dependence on the applied drain-to-source bias voltage of the transistor. This behaviour is explained by an amplification of the primarily generated photocurrent by traps in the buffer layer of the transistor. The occupation time of these traps can strongly depend on the applied voltage.