Effects of AlN/GaN superlattice buffer layer on performances of AlGaN/GaN HEMT grown on silicon for sub-6 GHz applications

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 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 cm(2) (V s)(-1)) as well as two-dimensional electron gas concentration (1.04 x 10(13) 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(-1) at V (GS) = 0 V and a low on-resistance of 4.3 +/- 0.15 omega 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 radio frequency (RF) applications. This GaN HEMT structure based on SL buffer layer is suitable for low-frequency RF power applications.