Characteristics of 2DEG generated at the heterointerface of an AlN/GaN structure grown on an AlN substrate using metal organic vapor phase epitaxy

Abstract

A pseudomorphic AlN/GaN structure was grown on an AlN substrate using metalorganic vapor phase epitaxy (MOVPE). The Hall effect characteristics of two-dimensional electron gas induced at the interface between AlN and GaN and the properties of high-electron-mobility transistors (HEMTs) fabricated using the proposed AlN/GaN structures were investigated. The Hall effect measurements indicated that the electron mobility at room temperature was 294 cm2 V−1 s−1, the sheet carrier density was 1.1 × 1013 cm−2, and the sheet resistance was 1930 Ω/sq. Cross-sectional transmission electron microscopy images revealed an extremely abrupt interface between the AlN and GaN layers. By contrast, surface atomic force microscopy measurements indicated that GaN exhibited a clear step-terrace surface and the AlN barrier layer exhibited the signs of transitioning to island-like growth. Furthermore, the HEMT devices exhibited clear transistor characteristics with a source–drain breakdown voltage of 2.3 kV and an ON/OFF ratio of >107. These findings demonstrate the potential of MOVPE for fabricating AlN/GaN on AlN substrates, showing the inherent potential of AlN as a substrate.