Controlled crystal orientations of semipolar AlN grown on an m-plane sapphire by MOCVD

Abstract

The way to control AlN orientations on an m-plane sapphire in metal-organic chemical vapor deposition has not been clarified. We investigated the effect of the nitridation process on the crystal orientation of semipolar AlN on an m-plane sapphire. In terms of substrate heating, (10-1-3) AlN was obtained under H2 without NH3, whereas (11–22) AlN was obtained by heating with H2 and NH3. Temperature-dependent nitridation demonstrated that the AlN orientation changed from (10-1-3) to (11–22) at the nitridation temperature of 500 °C, which can be explained by the formation of r-plane nanofacets on m-plane sapphire under significant nitridation at a high temperature. At a nitridation temperature of 1100 °C, a small amount of NH3 led to the formation of (11–22) AlN, indicating that care must be taken to keep the reactor conditions for producing desired AlN orientations with reproducibility.