Electron mobility exceeding 160 000 cm{sup 2}/V s in AlGaN/GaN heterostructures grown by molecular-beam epitaxy

We report on the transport properties of a two-dimensional electron gas (2DEG) confined in an AlGaN/GaN heterostructure grown by plasma-assisted molecular-beam epitaxy on a semi-insulating GaN template prepared by hydride vapor phase epitaxy with a threading dislocation density of {approx}5x10{sup 7} cm{sup -2}. Using a gated Hall bar structure, the electron density (n{sub e}) is varied from 4.1 to 9.1x10{sup 11} cm{sup -2}. At T=300 mK, the 2DEG displays a maximum mobility of 167 000 cm{sup 2}/V s at a sheet density of 9.1x10{sup 11} cm{sup -2}, corresponding to a mean-free-path of {approx}3 {mu}m. Shubnikov-de Haas oscillations, typically not observed at magnetic fields below 2 T in GaN, commence at B=0.6 T.