p-GaN Gate HEMT With Surface Reinforcement for Enhanced Gate Reliability

By deploying a surface reinforcement layer (SRL) at the interface between Schottky metal and {p} -GaN in the gate stack, a {p} -GaN gate high-electron-mobility transistor (HEMT) with enhanced gate reliability is demonstrated. Prior to the gate metal deposition, the SRL is formed by an oxygen-plasma treatment and a subsequent high-temperature annealing process (at 800 °C) that enables surface reconstruction. Such a process converts several nanometers of {p} -GaN near the surface into a crystalline GaON layer, which exhibits stronger immunity to hot electron bombardment. With nearly identical threshold voltage and ON -resistance, the {p} -GaN gate HEMT with SRL yields two orders of magnitude reduction in gate leakage current at ON -state and an increase from 10.5 V to 12.7 V in forward gate breakdown voltage. Time-dependent gate breakdown measurement reveals an increase from 5.9 V to 7.8 V in the maximum ON -state gate drive voltage for a 10-year lifetime with a 1 % gate failure rate, which effectively expands the operating voltage margin of the {p} -GaN gate power HEMT.