Microwave characteristics of a pseudomorphic high electron mobility transistor under electro-optical stimulations

Comprehensive P-opt-, V-GS-, and V-DS-dependent variations of microwave per formances (f(T) and f(max)) in a PHEMT under electro-optical stimulation ar e reported for the first time. Under low P-opt, microwave characteristics a re observed to be predominantly modulated by the photoconductive effect thr ough the transconductance, Under high optical power, however, they are limi ted by the photovoltaic effect through the gate capacitance and a parasitic MESFET activated parallel to the In0.13Ga0.87As channel PHEMT, Contrary to the dc current-voltage (I-V) characteristics, which are predominantly cont rolled by the photoconductive effect with a strong nonlinearity due to a pa rallel conduction, microwave characteristics strongly depend on the photovo ltaic effect as well as the photoconductive effect under electro-optical st imulation. An extended small-signal photonic-microwave model is suggested f or better description of PHEMT's under electro-optical stimulations.