; Key Laboratory of Acoustic and Photonic Materials and Devices, Ministry of Education, and School of Physics and Technology, Wuhan University, Wuhan 430072, People’s Republic of China
Liu, C. more authors
Al0.30Ga0.70N/GaN heterostructures grown on sapphire substrates by rf-plasma-assisted molecular beam epitaxy are investigated. The heterostructures consist of a 20nmAl0.30Ga0.70N barrier layer deposited on a 2μm semi-insulating GaN epilayer. Room-temperature mobilities averaging 1350cm2/Vs and a sheet charge density of 1.1×1013cm-2 are consistently achieved. Central to our approach is the iron-doped semi-insulating GaN epilayer and a pulsed N/Ga atomic deposition technique which makes it possible to simultaneously reduce threading dislocations and achieve a smooth surface. The heterostructures were examined by x-ray diffraction, transmission electron microscopy, and atomic force microscopy. Structural characterizations reveal a smooth surface morphology, coherent and sharp interfaces, and a low density of the threading dislocations.