Growth of semi-polar [formula omitted] GaN on m-plane sapphire via In-Situ Multiple Ammonia Treatment (I-SMAT) method

Abstract

Enhanced surface morphological properties of semi-polar (112¯2) gallium nitride (GaN) were successfully achieved via implementing an In-Situ Multiple Ammonia Treatment (I-SMAT) method. Utilization of an optimized flow of ammonia (1 SLM), surface striations of semi-polar (112¯2) GaN was reduced yielding RMS roughness of 4.20 nm. Low scan sizes of the surface reveal an evolution of the atomic-sized terraces to a rather uniformly arranged distribution resulting in narrowing/shallowing of the interfacial valleys. X-ray rocking curve (XRC) analysis implies that I-SMAT would facilitate dislocation reduction through a selective-area etching process consequently enhancing the crystal quality. Conversely, excessive ammonia flux during the I-SMAT would degrade the structural and morphological properties of the semi-polar epilayer whereby the alternating thin GaN epilayer would undergo the selective-area etching to the extreme. This in turn exposes the etched sites significantly prior to the subsequent thick semi-polar (112¯2) GaN epilayer resulting in a polarity change in the crystal orientation.