Investigation of gate metal effects on barrier lowering, on-resistance, and breakdown voltage in p-GaN gate HEMTs

This study systematically examines the impact mechanisms of gate metal selection on the performance of p-GaN HEMT. Through comprehensive analysis combining gate-source capacitance characterization with output current density and on-resistance measurements at the gate/p-GaN interface, we reveal that the effective gate voltage applied to the AlGaN/GaN channel decreases with reducing metal work function, consequently leading to lower output current and higher on-resistance. Quantitative characterization shows average drain-induced barrier lowering coefficients of 2 mV/V, 22.2 mV/V, and 46.7 mV/V for Ni/p-GaN, Cu/p-GaN, and W/p-GaN HEMTs, respectively, with corresponding off-state breakdown fields of 0.62 MV/cm, 0.56 MV/cm, and 0.48 MV/cm. Numerical simulations and band diagram analyses consistently verify and elucidate the gate metal's impact on both drain-induced barrier lowering effects and off-state breakdown characteristics.