Defect reduction in non-polar (11(2)over-bar0) GaN grown on (1(1)over-bar02) sapphire

This work assesses the relative effectiveness of different techniques to reduce defect density in heteroepitaxial, non-polar, a-plane GaN films grown on r-plane sapphire by MOVPE. Plan view TEM was used to obtain the defect density of films grown by different methods. The as-grown material was found to have a high dislocation and basal plane stacking fault (BSF) density (1.9 (+/- 0.2) x 10(11) cm(-2) and 1.1 (+/- 0.9) x 10(6) cm(-1) respectively). The four defect reduction techniques tested were: 3D-2D growth, SiNx, interlayers, ScN interlayers and epitaxial lateral overgrowth (ELOG). Both dislocation and BSF density were reduced by all methods compared to the as-grown material. The lowest defect density was achieved in the (0001) wing of the ELOG sample and was <1 x 10(6) dislocations cm(2) and 2.0 (+/- 0.7) x 10(4) BSFs cm-1. On the wafer scale, ScN interlayers were most effective: A single 5 nm thick ScN interlayer reduced the BSF density to 5.9 (+/- 0.8) x 10(5) cm(-1) and the dislocation density was reduced by two orders of magnitude to 1.8 (+/- 0.2) x 109 cm(-2) compared to the as-grown material. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim