Microstructure of InN epilayers deposited in a close-coupled showerhead reactor

The microstructure of epitaxial InN layers has been analyzed by high-resolution X-ray diffraction. Various mosaic block parameters like the tilt and twist between the blocks and an estimate of their lateral coherence lengths have been obtained for a large number of InN epitaxial layers deposited under different V/III ratios, temperatures and reactor pressures. Based on the detailed analysis of the microstrain, we have arrived at a set of optimized deposition parameters for InN in a close-coupled showerhead reactor. We also conclude that excessively high V/III ratio, as mentioned in a few earlier reports, is not a prerequisite for the deposition of high-quality InN layers. In fact, all deposition parameters that lead to an increase in the dissociation of ammonia beyond a critical value lead to increase in the screw dislocation density as indicated by an increase in the tilt value. Interestingly, we find that the density of edge dislocation, indicated by the twist value of the epilayers remains nearly the same irrespective of the deposition parameters. (C) 2008 Elsevier B.V. All rights reserved.