Quantitative mobility spectrum analysis of AlGaN∕GaN heterostructures using variable-field hall measurements

Carrier transport properties of AlGaN∕GaN heterostructures have been analyzed with the quantitative mobility spectrum analysis (QMSA) technique. The nominally undoped Al0.08Ga0.92N∕GaN sample was grown by plasma-assisted molecular beam epitaxy on a GaN/sapphire template prepared with hydride vapor phase epitaxy. Variable-magnetic-field Hall measurements were carried out in the temperature range of 5–300K and magnetic field range of 0.01–7T. QMSA was applied to the experimental variable-field data to extract the concentrations and mobilities associated with the high-mobility two-dimensional electron gas and the relatively low-mobility bulk electrons for the temperature range investigated. The mobilities at T=80K are found to be 7100 and 880cm2∕Vs, respectively, while the corresponding carrier densities are 7.0×1011 and 8×1014cm−3. Any conclusions drawn from conventional Hall measurements at a single magnetic field would have been highly misleading.