Theory and Experiment for the GaAs MESFET under Optical Illumination

The effects of light on the DC and RF properties of MESFETs are predicted and measured. Photovoltaic effects in the region of the metal-semiconductor Schottky gate and in the interface between the active channel and substrate or buffer layer are considered, as well as photoconductive effects in the parasitic resistances at the ends of the channel. Some applications of optical illumination to the control of gain in MESFET amplifiers and to the stabilisation of frequency in MESFET oscillators are considered. These, together with the application of microwave-modulated light to the synchronisation (phase locking) of MESFET oscillators may well find considerable importance in monolithic microwave integrated circuits because of the ease of forming the control interface with monolithic chip.