High mobility two-dimensional electron gas in AlGaN/GaN heterostructures grown by plasma-assisted molecular beam epitaxy

Abstract

High quality AlGaN/GaN heterostructures have been grown by radio-frequency plasma-assisted molecular beam epitaxy on n-type GaN templates grown on sapphire by metal organic chemical vapor deposition. The unintentionally doped ${\mathrm{Al}}_{\mathrm{0.12}}{\mathrm{Ga}}_{\mathrm{0.88}}\mathrm{N/GaN}$ heterostructure exhibits a 77 K Hall mobility of 14 500 cm²/Vs and a 12 K mobility of 20 000 cm²/Vs ${\mathrm{(n}}_s{\text{=5.0×10}}^{12}\hspace{0.5em}{\mathrm{cm}}^{\mathrm{-2}}\mathrm{).}$ A room temperature mobility of 1860 cm²/Vs ${\mathrm{(n}}_s{\text{=4.8×10}}^{12}\hspace{0.5em}{\mathrm{cm}}^{\mathrm{-2}})$ was calculated for the two-dimensional electron gas channel using a two layer model from the measured mobility for the whole structure (template plus heterostructure). Magnetoresistance measurements at 4.2 K showed well-resolved Shubnikov–de Haas oscillations, which began at 2.6 T.