CHARGE COLLECTION MECHANISMS OF HETEROSTRUCTURE FETS

Ion- and laser-induced charge-collection transients measured for AlGaAs/InGaAs heterostructure insulated-gate field-effect transistors (HIGFETs) reveal evidence for two mechanisms of enhanced charge collection: a channel-modulation mechanism that dominates the charge-collection processes at positive gate biases and can persist for several nanoseconds; and a parasitic bipolar transistor mechanism that shows a sensitive dependence on the density of free carriers injected into the device, and is complete within a few hundred picoseconds. The results reinforce the utility of the laser technique for investigating the charge-collection mechanisms of semiconductor devices.