High-quality nonpolar 4H-AlN grown on 4H-SiC (11(2)over-bar20) substrate by molecular-beam epitaxy

Growth of very high-quality nonpolar (11 (2) over bar0) a-plane face 4H-AlN on 4H-SiC (11 (2) over bar0) substrate was investigated. Nonpolar 4H-AlN (11 (2) over bar0) was isopolytypically grown on 4H-SiC (11 (2) over bar0) substrate by molecular-beam epitaxy. A reduction of defects such as stacking faults and threading dislocations was achieved by keeping the growing surface flat. To this end, the SiC substrate was HCl gas etched and the V/III ratio was optimized for AlN growth. A full width at half maximum of symmetrical x-ray diffraction omega scan of the 4H-AlN layer was 40 arc sec. Transmission electron microscopy revealed the stacking fault density to be 2x10(5) cm(-1), and the partial and perfect threading dislocation densities to be 7x10(7) and 1x10(7) cm(-2), respectively. (c) 2006 American Institute of Physics.