AlGaN/AlN/GaN heterostructures were grown on 6H-SiC, GaN-on-sapphire, and free-standing GaN, resulting in heterostructures with threading dislocation densities of ∼2 x 1010, ∼5 x 108 and ∼5 x 107/cm2, respectively. Growths were carried out under Ga-rich conditions by plasma-assisted molecular beam epitaxy to determine the influence of threading dislocation density on the sheet resistance of AlGaN/AlN/GaN heterostructures. High threading dislocation density was observed to significantly degrade Hall mobility. An AlGaN/AlN/GaN heterostructure with a ∼2 nm AlN interlayer and a threading dislocation density of ∼5 x 107/cm2 achieved the very low room temperature sheet resistance of 175Ω/□.

Correlation between Threading Dislocation Density and Sheet Resistance of AlGaN/AlN/GaN Heterostructures Grown by Plasma-Assisted Molecular Beam Epitaxy. S.W.Kaun, M.H.Wong, U.K.Mishra, J.S.Speck: Applied Physics Letters, 2012, 100[26], 262102