Very low dislocation density, resistive GaN films obtained using transition metal nitride interlayers

Abstract

A threading dislocation density (TDD) reduction method for GaN films is described. Thin amorphous layer of Sc, Hf, Nb, Zr and Cr were deposited on MOVPE-grown GaN-on- sapphire templates with a TDD of 5 × 10 9 cm -2 and annealed in NH 3 to form metal nitrides. The ScN layer remained continues, with a very low pinhole density of approximately 3 × 10 9 cm -2. The NbN and ZrN layer formed oriented holey network structures. The Cr layer did not nitride. Coalesced GaN epilayers grown on the ScN layers had the lowest dislocation density of 3 × 10 7 cm -2 (un-coalesced GaN on ScN had TDDs as low as 5 × 10 6 cm -2). Unlike GaN films grown using multiple SiN x interlayers, which contain a similar proportion of edge and mixed dislocation, the GaN-on-ScN layers contain substantially fewer mixed than edge dislocation, a proportion similar to that of the high-TDD template. The low TDD GaN epilayers grown on ScN are also highly electrically resistive. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA.