Formation of ultra-high-resistance Au/Ti/p-GaN junctions and the applications in AlGaN/GaN HEMTs

We report a dramatic current reduction, or a resistance increase, by a few orders of magnitude of two common-anode Au/Ti/p-GaN Schottky junctions annealed within a certain annealing condition window (600–700 °C, 1–4 min). Results from similar common-anode Schottky junctions made of Au/p-GaN, Al/Ti/p-GaN, and Au/Ti/graphene/p-GaN junctions demonstrated that all three layers (Au, Ti, and p-GaN) are essential for the increased resistance. Scanning-transmission electron microscopy, Hall, and Raman measurements have been performed to investigate the mechanisms. Moreover, this high-resistance junction structure was employed in p-GaN gate AlGaN/GaN high electron mobility transistors. It was shown to be an effective gate technology that was capable of boosting the gate breakdown voltage from 9.9 to 12.1 V with a negligible effect on the threshold voltage or the sub-threshold slope.