Facet-control in selective area growth (SAG) of a-plane GaN by MOVPE

Abstract

Selective area growth (SAG) of a-plane GaN grown on r-plane sapphire with a stripe orientation along <1-100> was investigated. The key technology of facet-control is optimizing the growth temperature and the reactor pressure. Our experiments reveal that the growth temperature determined facet form: in samples grown at 1000 °C, the structure consists of {11-22}and (000-1); with increasing growth temperature to 1050 °C, the area of {11-22} facet gradually decreases, and two new planes, (0001) and {11-20} facets form; eventually, in samples grown at 1000 oC, the {11-22} facet completely disappears, (0001) and {11-20} facet continue to increase to form a rectangle cross-section. The reactor pressure determines the ratio of the lateral growth rate and the vertical growth rate: with reactor pressure decreasing from 500 torr to 100 torr, the rectangle structure gradually decreases the height and increases the width, and the volume nearly keeps constant.