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

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