INFLUENCE OF POLARIZATION CHARGES AND ELECTRON TRAPPING IN THE BUFFER LAYER IN WURTZITE PHASE AlGaN/GaN HFETs

Ensemble Monte Carlo simulations have been performed to model electron transport in wurtzite phase AlGaN/GaN heterojunction FETs. Planar Al0.2Ga0.8N/GaN HFET structures with a 78 nm Al0.2Ga0.8N pseudomorphically strained layer were simulated, where the spontaneous and piezoelectric polarization effects were taken into account. Trap centers located in the buffer layer has also been simulated to include the effect of trapping levels on current collapse in GaN HFETs. The polarization effects was shown to not only increase the current density, but also improve the electron transport in the interface layer by inducing a higher electron density to the positive polarized sheet and away from the buffer layer.