Monte Carlo study of the dynamic breakdown effects in HEMT's

We present a theoretical investigation of the near-breakdown scenario in pseudomorphic high electron mobility transistors (HEMT's). We show that the main mechanism for the enhanced drain current is a parasitic bipolar effect due to holes, generated by impact ionization, which accumulate in the channel and in the substrate close to the source contact. The dynamic of this charge accumulation and of the consequent drain current increase is studied by means of a two-dimensional (2-D) Poisson Monte Carlo simulator.