Mobility enhancement of 2DEG in MOVPE-grown AlGaN/AlN/GaN HEMT structure using vicinal (0 0 0 1) sapphire

Al0.25Ga0.75N/AlN/GaN high electron mobility transistor (HEMT) structures were grown on (0 0 0 1) sapphire substrates with vicinal angles of 0.0∘,0.25∘,0.5∘ and 1.0∘ by metalorganic vapor phase epitaxy (MOVPE). Vicinal sapphire was demonstrated to enhance the step-flow growth to improve morphology, crystal and optical qualities, which eventually suppressed interface scattering and dislocation scattering to enhance the mobility of 2-dimension-electron-gas (2DEG). The optimum vicinal degree was determined to be 0.5∘, and the corresponding 300 K Hall mobility and sheet resistance were 1720 cm2/V s and 301 Ω/sq, respectively. Furthermore, the temperature dependence of Hall measurements proved good high-temperature performance of the 0.5-off sample.