Ionization-induced carrier transport in InAlAs/InGaAs high electron mobility transistors

Time resolved charge-collection measurements and two-dimensional device simulations performed on InAlAs/InGaAs high electron mobility transistors (HEMTs) for ion and pulsed laser excitation address the mechanisms of charge collection and enhancement in these heterostructure devices. The results are compared to those for bulk GaAs field-effect transistors. In the HEMTs, the ionization-induced enhancement current is associated with a significant lowering of the source/channel barrier, and is largely confined to the InGaAs well. The simulations suggest that the primary contributor to the barrier lowering is an excess hole density that develops in the InAlAs buffer layer.