Progress in the growth of nonpolar gallium nitride

The active regions of conventional c-plane (Al,ln,Ga)N optoelectronic devices suffer from deleterious polarization effects. These polarization effects can be eliminated by growing devices on alternative GaN planes, such as {1 (1) over bar 00} m-plane or {1 1(2) over bar 0} a-plane films. Previous attempts to grow nonpolar GaN by vapor phase and molecular beam epitaxy methods yielded rough and faceted surfaces that were unsuitable for device use. Beginning with Waltereit et al.'s work [Nature, 406, 865 (2000)], significant progress has been made in improving nonpolar GaN structural quality and morphology. This paper reviews the structural and morphological characteristics of planar, nonpolar a-plane and m-plane GaN films grown by vapor phase and molecular beam epitaxy techniques. Defect reduction via lateral epitaxial overgrowth, and the influence of extended defects on surface morphology will be further discussed. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.