Experimental Verification of Substrate Bias Effect on the Gate Charge for GaN HEMTs

Gate charge (Q
_g
) of GaN power devices under different substrate biases are investigated for the first time. The devices under test are subjected to pulse-mode stress similar to circuit switching conditions. Compared with a grounded substrate, injected electrons interacting with the buffer traps lead to a significant decrease in Q
_g
under a negative substrate bias. On the other hand, ionized donor-like traps in the buffer layer induce an increase in Q
_g
under a positive substrate bias.