Development of high-performance nonpolar III-nitride light-emitting devices

Growth of InGaN/GaN light-emitting devices on nonpolar planes offers a viable approach to eliminating the issues associated with polarization-related electric fields present in c-plane III-nitride heterostructures. Although progress in device performance has been rapid since the introduction of high-quality free-standing nonpolar substrates, a full appreciation of the materials challenges unique to nonpolar III-nitride semiconductors has been slower to emerge. Only recently have researchers begun to understand issues such as the origins of the pyramidal hillocks typically observed on nominally on-axis m-plane GaN films, the effects of m-plane substrate misorientation on surface morphology, and the effects of m-plane substrate misorientation on device performance. In this article, we review the materials and growth issues unique to high-performance nonpolar light-emitting devices grown on high-quality free-standing substrates and provide an outlook for the opportunities and challenges that lie ahead.