Gate Characteristics of Enhancement-Mode Fully Depleted p-GaN Gate HEMT

The conventional p -GaN in Schottky-type p -GaN gate HEMTs is converted into an insulator-like p -GaN, i.e., fully depleted p -GaN in the reverse-biased Schottky junction under forward gate bias ( V GS ), by inadequate activation of Mg. Consequently, the gate current ( I G ) is reduced by 3 – 5 orders of magnitude at VGS of 7 V over a temperature range of 25 °C – 150 °C, compared with devices adopting conventional adequate activation. The fully depleted p -GaN converts the current-balance-based forward V GS division in the conventional partially depleted p -GaN gate stack, into thickness-based voltage division in p -GaN and AlGaN between gate and channel, which is like that in a MIS (metal-insulator-semiconductor) gate. As a result, the hole current through the Schottky junction is significantly reduced while the electron spillover current starts to dominate at high forward V GS . Besides, hot carriers are excluded from the forward gate breakdown mechanism.