Detrapping Kinetics in N-Polar AlGaN/GaN MIS-HEMTs

Abstract

We investigated the influence of aluminium concentration in the AlGaN cap layer on the stability of threshold voltage under gate and drain stress voltages. We found an empirical model that describes the de-trapping transients after a gate and drain stress in off-state condition. The devices examined are N-polar GaN MIS-HEMTs with a 2.6nm layer of Al x Ga 1-x N cap under the gate contact. The devices have three different Al concentration (x=22%, x=34%, x=46%) in the AlGaN cap layer. DC measurements show that the devices with a higher Al concentration have a lower gate leakage current. In this work we found out: 1) the amount of threshold voltage shift during stress in these devices, increases linearly with the value level of gate leakage current at the different bias conditions 2) a higher Al percentage in AlGaN cap layer can suppress gate leakage current and thus reduce the instability of threshold voltage under high gate and drain filling voltages.