Monte Carlo study of kink effect in short-channel InAlAs/InGaAs high electron mobility transistors

A semiclassical two-dimensional ensemble Monte Carlo simulator is used to perform a physical microscopic analysis of the kink effect in short-channel InAlAs/InGaAs lattice-matched high electron mobility transistors (HEMTs). Due to the small band gap of InGaAs, these devices are very susceptible to suffer impact ionization processes, with the subsequent hole transport in the channel, both supposedly implicated in the kink effect and easy to be implemented in a Monte Carlo simulation. The results indicate that for high enough $VDS,$ holes, generated by impact ionization, tend to pile up in the channel under the source side of the gate due to the attracting potential caused by the surface charge at the recess and, mostly, by the gate potential. Due to this pile up of positive charge, the potential barrier controlling the current through the channel is lowered, so that the channel is further opened and $ID$ increases, leading to the well known kink effect in the current–voltage characteristics. The microscopic understanding of this phenomenon provides valuable information to conceive the optimum fabrication process for kink-effect-free HEMTs.