Correlation between threading dislocation density and sheet resistance of AlGaN/AlN/GaN heterostructures grown by plasma-assisted molecular beam epitaxy

AlGaN/AlN/GaN heterostructures were grown on 6H-SiC, GaN-on-sapphire, and free-standing GaN, resulting in heterostructures with threading dislocation densities of similar to 2 x 10(10), similar to 5 x 10(8), and similar to 5 x 10(7) cm(-2), 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 similar to 2 nm AlN interlayer and a threading dislocation density of similar to 5 x 10(7) cm(-2) achieved the very low room temperature sheet resistance of 175 Omega/square. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4730951]