Comparative study on thermal robustness of GaN and AlGaN/GaN MOS devices with thin oxide interlayers

Abstract

Similarities and differences in the design of the interfaces between gate dielectrics and GaN-based semiconductors were systematically investigated with a focus on the thermal stability of the interlayers. Although the excellent electrical properties of a SiO2/GaN interface with a thin Ga-oxide interlayer (SiO2/GaOx/GaN) were deteriorated by high-temperature treatment at around 1000 °C, the thin oxide on the AlGaN surface (SiO2/GaOx/AlGaN) exhibited superior thermal stability and interface quality even after treatment at 1000 °C. Physical characterizations showed that thermal decomposition of the thin GaOx layer on the GaN surface is promoted by oxygen transfer, which produces volatile products, leading to remarkable roughening of the GaN surface. In contrast, decomposition of the thin GaOx layer was suppressed on the AlGaN surface under the high temperatures, preserving a smooth oxide surface. The mechanisms behind both the improved and degraded electrical properties in these GaN-based MOS structures are discussed on the basis of these findings.