Investigations of the gate instability characteristics in Schottky/ohmic type p-GaN gate normally-off AlGaN/GaN HEMTs

Abstract

In this work, the impacts of Schottky- and ohmic-type gate contacts on devices stability of p-GaN gate AlGaN/GaN high electron mobility transistors were experimentally investigated. In the Schottky-gate devices, drastic gate instability were observed under positive gate bias and elevated temperatures, featuring evident negative threshold voltage shift especially at low gate voltage region. By contrast, ohmic-gate devices exhibit superior gate stability with near-zero threshold voltage shift. Correspondingly, a physics picture of hole injection/emission processes in the p-GaN layer was established for the understanding of the distinct gate stability behaviors with different gate contact types.