This paper reports on the behavior of Al/Ti/ p-GaN interfaces as gate contacts for p-GaN/AlGaN/GaN normally off high electron mobility transistor (HEMTs), highlighting the impact of the thermal budget on the metal gate on the device characteristics. In fact, while the devices subjected to an annealing at 800°C show a considerable high leakage current, those with nonannealed Al/Ti gate contacts exhibit a normally off behavior, with a pinch-off voltage V po = +1.1 V and an on/off current ratio of 3 × 10 8 . Temperature-dependent electrical measurements on back-to-back Schottky diodes allowed to determine a Schottky barrier height Φ B of 2.08 and 1.60 eV, for the nonannealed and 800°C annealed gate contacts, respectively. Hence, the increase in the leakage current observed upon annealing at 800°C was attributed to the lowering of the Schottky barrier height Φ B of the metal gate. The interfacial structural …