InGaN/(GaN)/AlGaN/GaN normally-off metal-oxide-semiconductor high-electron mobility transistors with etched access region

Abstract

The proposal and processing aspects of the prove-of-concept InGaN/GaN/AlGaN/GaN metal-oxide-semiconductor (MOS) high-electron mobility transistor with etched access regions are addressed. Full strain and decent quality of the epitaxial system comprising 4 nm In0.16Ga0.84N/3 nm GaN/5 nm Al0.27Ga0.73N are observed using a high-resolution transmission-electron microscopy and by deformation profile extractions. Large negative polarization charge in the MOS gate stack provides the HEMT normally-off operation, while free electrons are populated at access regions after etching. Consecutive passivation by 10 nm Al2O3 together with annealing at 300 °C improved the Al2O3/semiconductor interface, with the threshold voltage (VT) reaching 1 V. Improvements of the present concept in comparison to the previous one with a gate recess were proved by showing the decreased drain leakage current and increased breakdown voltage.