CHARGE COLLECTION MECHANISMS OF HETEROSTRUCTURE FETS

Ion- and laser-induced charge-collection transients measured for AlGaA s/InGaAs heterostructure insulated-gate field-effect transistors (HIGF ETs) reveal evidence for two mechanisms of enhanced charge collection: a channel-modulation mechanism that dominates the charge-collection p rocesses at positive gate biases and can persist for several nanosecon ds; and a parasitic bipolar transistor mechanism that shows a sensitiv e dependence on the density of free carriers injected into the device, and is complete within a few hundred picoseconds. The results reinfor ce the utility of the laser technique for investigating the charge-col lection mechanisms of semiconductor devices.