Trap-Related Current Collapse Effects in GaN HEMTs

The current collapse effects are investigated in GaN HEMTs by means of dc and dynamic measurements. The trapping-detrapping process is demonstrated by varying the hold time from 0.1s to 20s and the delay time from l0us to l00ms. The relevant time constant is more than ls. Our simulation result show that the gate-induced collapse is related both to the high surface state density and high vertical electric filed. New structures are simulated to demonstrate the advantages in reducing both gate-induced and buffer-induced collapse.