Dependency of current collapse on the device structure of GaN-based HEMTs

Pulse transient simulation is very useful for analyzing the mechanism of dynamic current collapse in GaN-based HEMTs. In this paper, the dependency of current collapse on the device structure is analyzed based on the two-dimensional numerical simulation. The turn-on pulse gate-lag transient currents of Al _0.3 Ga _0.7 N/GaN HEMTs with different gate lengths and drain-source distances were obtained, and the results show that current collapse is dependent on the device dimensions, i.e. small-scale devices suffer from larger current collapse due to the stronger electric field. The current collapse caused either by surface trapping effect or by bulk trapping effect increases with the gate length decreasing. However, due to the interaction between the bulk and surface trapping effects, the total current collapse may be reduced for the GaN-based devices.