AlGaN/GaN high electron mobility transistors (HEMTs) heterostructures are grown by metal-organic chemical vapor deposition (MOCVD) on silicon-on-insulator (SOI) substrate and high resistive (HR-Si) simultaneously to investigate the influence of substrate types on electrical and thermal characteristics. The AlGaN/GaN HEMT epitaxial structure grown on SOI achieved high electron mobility (1900±19 cm2/V·s) and high two-dimensional electron gas (2DEG) carrier concentration (9.1±0.1×1012/cm2). The GaN HEMT metal-insulator-semiconductor gate (MIS-HEMT) device fabricated on the structure grown on the SOI substrate exhibits higher saturation current and improved buffer breakdown voltage compared with devices fabricated on high-resistivity silicon (HR-Si) substrate. In particular, SOI substrate helps to improve the thermal-sensitive strain of the GaN-based heterostructure and reduced defect density in the epitaxy, thereby improve the temperature-dependent on-resistance (RON) and the dynamic RON of the device.

In this study, the effects of AlN/GaN superlattice (SL) thickness on performances of AlGaN/GaN high electron mobility transistor (HEMT) heterostructure grown by metal-organic chemical vapor deposition (MOCVD) on silicon is investigated. Stress in GaN is controlled by varying the total thickness of the AlN/GaN SL. Improved crystal quality and surface roughness accomplished with 2200 nm-thick AlN/GaN SL, leads to an increase in high electron mobility (1760 cm2/V·s) as well as two-dimensional electron gas (2DEG) concentration (1.04×1013 cm-2). AlGaN/GaN metal-insulator-semiconductor HEMT (MIS-HEMT) fabricated on the heterostructure with SL buffer layer exhibits a significant improvement in maximum saturation current of 1100±29 mA/mm at VGS = 0 V and a low on-resistance (RON) of 4.3±0.15 Ω·mm for the optimized AlN/GaN SL. The 2200 nm-thick AlN/GaN SL supports the growth of stress-free GaN heterostructure, which can reduce the insertion loss for sub-6 GHz RF applications. This GaN HEMT structure based on superlattice buffer layer is suitable for low-frequency RF power applications.