High electron mobility in AlGaN/GaN heterostructures grown on bulk GaN substrates

Dislocation-free high-quality AlGaN/GaN heterostructures have been grown by molecular-beam epitaxy on semi-insulating bulk GaN substrates. Hall measur ements performed in the 300 K-50 mK range show a low-temperature electron m obility exceeding 60 000 cm(2)/V s for an electron sheet density of 2.4x10( 12) cm(-2). Magnetotransport experiments performed up to 15 T exhibit well- defined quantum Hall-effect features. The structures corresponding to the c yclotron and spin splitting were clearly resolved. From an analysis of the Shubnikov de Hass oscillations and the low-temperature mobility we found th e quantum and transport scattering times to be 0.4 and 8.2 ps, respectively . The high ratio of the scattering to quantum relaxation time indicates tha t the main scattering mechanisms, at low temperatures, are due to long-rang e potentials, such as Coulomb potentials of ionized impurities. (C) 2000 Am erican Institute of Physics. [S0003-6951(00)01042-1].