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 degrees C-150 degrees 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 VGS. Besides, hot carriers are excluded from the forward gate breakdown mechanism.