Step-flow MOVPE of GaN on SiC substrates

Abstract

Step-flow MOVPE of GaN on SiC substrates is confirmed by AFM observation. Compared to the growth on sapphire substrates, there are no step terminations and no 2D nuclei within a 10 micron square area, showing step-flow mode is dominant. The surface mostly consists of 190-nm-wide atomic terraces and 0.6-nm-high doubly stacked monolayers (DSM) along [1 1 2 ̄ 0]. This DSM dissolves into a pair of monolayers at the adjacent DSM steps, due to the asymmetry between these two monolayers which have different bond configurations at the step edge. By the homogeneity of step-flow growth, FWHMs of about 100 arcsec in X-ray locking curve and sharp photoluminescence (FWHM: 20 meV) from 1.1-nm-thick GaN/AL 0.15Ga 0.85N quantum well are obtained. We also found, in finite area selective epitaxy (FAE), steps originate from a single 2D nucleus, which shows heterointerface flatness will be significantly improved by using the combination of SiC substrates and FAE.