Total current collapse in high-voltage GaN MIS-HEMTs induced by Zener trapping

We investigate current collapse in GaN MIS-HEMTs for >600 V operation. Extreme trapping leading to total current collapse has been observed after OFF-state stress at high voltage. We attribute this to high-field tunneling-induced electron trapping (“Zener trapping”) inside the AlGaN barrier or the GaN channel layers. The trapping takes place in a narrow region right under the edge of the outermost field plate in the drain portion of the device. The trapping characteristics are consistent with those responsible for the yellow luminescence band in GaN or AlGaN. This finding gives urgency to defect control during epitaxial-growth and the design of appropriate field plate structures for the reliable high-voltage operation of MIS-HEMTs.