We present a comprehensive study on metal-organic vapor phase epitaxy growth of N-polar and Al-polar AlN on 4H-SiC with 4 degrees miscut using constant growth parameters. At a high temperature of 1165 degrees C, N-polar AlN layers had high crystalline quality whereas the Al-polar AlN surfaces had a high density of etch pits. For N-polar AlN, the V/III ratio below 1000 forms hexagonal hillocks, while the V/III ratio over 1000 yields step bunching without the hillocks. 1-mu m-thick N-polar AlN layer grown in optimal conditions exhibited FWHMs of 307, 330 and 337 arcsec for (0 0 2), (1 0 2) and (2 0 1) reflections, respectively. (C) 2018 Elsevier B.V. All rights reserved.