Self-heating and trapping effects in AlGaN/GaN heterojunction field-effect transistors

Abstract

This work first attempted to simulate the band edges of AlGaN/GaN high electron mobility transistors (HEMTs) structures with Ga-face polarity at the heterointerface. The spontaneous and piezoelectric-induced polarization fields as well as the effects of temperature on the electron band parameters have been included into the modeling. In a second step, we calculated self-consistently direct-current characteristics of AlGaN/GaN HEMTs without considering any defect. Calculations were made as a function of doping concentration and Al composition. In the paper, the self-heating in AlGaN/GaN HEMTs grown on SiC substrate before and after Si3N4 passivation was also investigated revealing that: (i) power dissipation is induced due to the increase in drain bias, which leads to a temperature rise of the two-dimensional electron gas in the channel, (ii) an enhancement in drain current is achieved after Si3N4 passivation, (iii) the self-heating occurs even in AlGaN/GaN heterostructures after passivation. Including thermal and trapping effects in transistor device model can allow adjusting of some of the electron transport parameters in order to obtain optimized current at the output.