Photoinduced instability in microwave excited GaAs MESFETs

A photoinduced low frequency oscillation (LFO) is observed in GaAs MESFETs under microwave excitation at room temperature. The phenomenon is a self-sustained externally driven output power amplitude modulation and occurs within a range of light intensity, microwave power excitation level, and quiescent bias state. The oscillation frequency depends on the light intensity and microwave power, varying from 0.1 to 100 Hz. This oscillation phenomenon is found to be a strong function of device surface condition.