Electron mobility exceeding 160,000cm2/Vs 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 ~5x107cm-2. Using a gated Hall bar structure, the electron density (ne) is varied from 4.1 to 9.1x1011cm-2. At T=300mK, the 2DEG displays a maximum mobility of 167,000cm2/Vs at a sheet density of 9.1x1011cm- 2. This is the highest mobility reported for electrons in GaN to date, corresponding to a mean free path length of ~3mm at low temperatures. Shubnikov-de Haas oscillations, typically not observed at magnetic fields below 2 Tesla in GaN, commence at B = 0.6T. At low electron density, the n=2 integer quantum Hall state is observed at 8.5T.