Physical origin of kink in GaN HEMTs

The kink in the source-drain current of GaN devices has been not clarified. Based on the Maxwell-Boltzmann distribution of hot channel electrons, the generation of excess carriers in the L valleys of GaN and the origin of the kink had been modeled. This proposed model can predict how the kink depends on the gate voltage in experiments. It provides the reason why the kink partially disappears or disappears by sweeping the source-drain voltage from high voltage to low voltage, disappears under illumination, is more obvious at a lower temperature, and can be affected by different traps. All above experimental phenomena are associated with excess carriers in the L valleys of gain due to the hot channel carrier via internal transport. This model gives physical insight into how physical parameters of GaN devices affect the kink in the source-drain current. Thus, it can be used to optimize the physical parameters of GaN devices for reducing the kink.