Evidence of Hot-Electron Effects during Hard Switching of AlGaN/GaN HEMTs

This paper reports on the impact of soft- and hard-switching conditions on the dynamic ON-resistance of AlGaN/GaN high-electron mobility transistors. For this study, we used a special double pulse setup, which controls the overlapping of the drain and gate waveforms (thus inducing soft and hard switching), while measuring the corresponding impact on the ON-resistance, drain current, and electroluminescence (EL). The results demonstrate that the analyzed devices do not suffer from dynamic RON increase when they are submitted to soft switching up to VDS= 600 V. On the contrary, hard-switching conditions lead to a measurable increase in the dynamic ON-resistance (dynamic-RON). The increase in dynamic RON induced by hard switching is ascribed to hot-electrons effects: during each switching event, the electrons in the channel are accelerated by the high electric field and subsequently trapped in the AlGaN/GaN heterostructure or at the surface. This hypothesis is supported by the following results: 1) the increase in RON is correlated with the EL signal measured under hard-switching conditions and 2) the impact of hard switching on dynamic RON becomes weaker at high-temperature levels, as the average energy of hot electrons decreases due to the increase scattering with the lattice.