Growth of AlGaN and AlN on patterned AlN/sapphire templates

Published in:
J. Cryst. Growth, vol. 315, no. 1, pp. 200-203 (2011).
© 2011 Elsevier B.V. All rights reserved. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the Elsevier B.V.

Abstract:
Maskless epitaxial overgrowth of AlGaN on structured AlN templates was performed and the impact of stripe orientation on the lateral growth of AlGaN was studied. AlN/sapphire templates were patterned into stripes with 1.5 µm wide bars and a period of 3 µm. AlGaN and AlN growths were performed on the patterned templates. Two stripe orientations were investigated: stripes parallel to the [1100] and parallel to the [1120] directions. Coalescence was achieved for both stripe orientations. AlGaN layers grown on stripes oriented along the [1100] direction show a flat and closed surface in contrast to overgrown stripes oriented along the [1120] direction where the surface is facetted and rough. The Al content is strongly dependent on the growth facet and varies between 25% at the sidewalls and 50% on the c-facet. The overgrowth of stripes parallel to the [1100] direction with AlN shows coalescence and flat surfaces. The X-ray rocking curve full width at half-maximum of the [1012] reflection is reduced from 1000 arcsec to 500 arcsec for the overgrown AlN. Temperature dependent photoluminescence measurements of AlGaN:Si grown on these coalesced AlN templates also indicate a dislocation density reduction via this method.

Keywords:
A3. Metalorganic vapor phase epitaxy, A3. Pendeoepitaxy, A3. Epitaxial lateral overgrowth, B1. AlGaN, B1. Nitrides

Full version in pdf-format.