A study was made of the structural and electrical properties of AlGaN/GaN heterostructures grown by molecular beam epitaxy on low-dislocation-density, free standing GaN substrates grown by hydride vapor phase epitaxy. Structural characterization by atomic force microscopy, transmission electron microscopy, and X-ray diffractometry reveal a smooth surface morphology, coherent interfaces, an absence of dislocations generated in the epitaxial layers, and narrow X-ray peaks. Hall measurements indicated room temperature electron mobilities of 1750cm2/Vs at sheet densities of 1.1 x 1013/cm2. High electron mobility transistors exhibited excellent electrical characteristics, including output power densities of 4.8W/mm at 10GHz, off-state breakdown voltages of up to 200V, and extrinsic cut-off frequencies of 36GHz on devices with 0.45μm gate lengths.

Microwave Performance and Structural Characterization of MBE-Grown AlGaN/GaN HEMTs on Low Dislocation Density GaN Substrates. D.F.Storm, D.S.Katzer, J.A.Roussos, J.A.Mittereder, R.Bass, S.C.Binari, L.Zhou, D.J.Smith, D.Hanser, E.A.Preble, K.R.Evans: Journal of Crystal Growth, 2007, 305[2], 340-5