Monte Carlo study of kink effect in isolated-gate InAs/AlSb High Electron Mobility Transistors

A semiclassical 2D ensemble Monte Carlo simulator is used to perform a physical microscopic analysis of kink effect in InAs/AlSb High Electron Mobility Transistors (HEMTs). Due to the small bandgap of InAs, these devices are very susceptible to suffer impact ionization processes, with the subsequent hole transport through the structure, both implicated in the kink effect. The results indicate that, for high enough VDS, holes generated by impact ionization tend to pile up in the buffer (at the gate-drain side) due to the valence-band energy barrier between the buffer and the channel. Due to this accumulation of positive charge the channel is further opened and ID increases, leading to the kink effect in the I-V characteristics and even to the device breakdown. The microscopic understanding of this phenomenon provides useful information for a design optimization of kink-effect-free InAs HEMTs.