Channel thickness dependence of breakdown dynamic in InP-based lattice-matched HEMTs

We have investigated, by using Monte Carlo simulations, the effects of channel thickness on the breakdown dynamics in InP-based lattice-matched HEMTs (LM-HEMTs). Breakdown is due to the parasitic bipolar action of holes generated by impact ionization and accumulated in the low electric field regions near the source. Our results show that channel shrinking results in an increase in time-to-breakdown values due to holes real-space-transfer effects occurring in thin channel devices. The breakdown behavior of thin-channel devices (channel thickness ≤20 nm) is dominated by the accumulation of holes in the InAlAs buffer layer; in thick-channel devices breakdown is due to the parasitic bipolar action of holes accumulating in the InGaAs channel. These results suggest a frequency dependence of breakdown which can be relevant for power rf device applications and/or in the study of device survivability to rf overstress.