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

Abstract

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/GaO x /GaN) were deteriorated by high-temperature treatment at around 1000 °C, the thin oxide on the AlGaN surface (SiO2/GaO x /AlGaN) exhibited superior thermal stability and interface quality even after treatment at 1000 °C. Physical characterizations showed that thermal decomposition of the thin GaO x 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 GaO x 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.