Investigation of the interface properties of MOVPE grown AlGaN/GaN high electron mobility transistor (HEMT) structures on sapphire

Abstract We have developed a virtual GaN substrate on sapphire based on a two-step growth method. By optimizing the growth scheme for the virtual substrate we have improved crystal quality and reduced interface roughness. Our Al 0.22 Ga 0.78 N/GaN HEMT structure grown on the optimized semi-insulating GaN virtual substrate, exhibits Hall mobilities as high as 1720 and 7350 cm 2 /Vs and sheet carrier concentrations of 8.4 × 1012 and 10.0 × 1012 cm − 2 at 300 K and 20 K, respectively. The presence of good AlGaN/GaN interface quality and surface morphology is also substantiated by X-Ray reflectivity and Atomic Force Microscopy measurements. A simplified transport model is used to fit the experimental Hall mobility.