Electronic transport characterization of AlGaN∕GaN heterostructures using quantitative mobility spectrum analysis

Resistivity and Hall effect measurements in nominally undoped Al0.25Ga0.75N∕GaN heterostructures grown on sapphire substrate by metal-organic chemical vapor deposition are carried out as a function of temperature (20–350K) and magnetic field (0–1.5T). The measurement results are analyzed using the quantitative mobility spectrum analysis techniques. It is found that there is strong two-dimensional electron gas localization below 100K, while the thermally activated minority carriers with the activation energies of ∼58 and ∼218meV contribute to the electron transport at high temperatures.