Sublimation epitaxy of AlN on SiC: growth morphology and structural features

Abstract

In order to study the development of individual AlN crystallites, sublimation epitaxy of AlN was performed on 4H-SiC, off-axis substrates in an inductively heated setup. Growth process variables like temperature, extrinsic nitrogen pressure and time were changed in an attempt to favor the lateral growth of individual AlN crystallites and thus open possibilities to prepare continuous patterns. Scanning and transmission electron microscopy and cathodoluminescence were used to obtain plan-view and cross-sectional images of the grown patterns and to study their morphology and structural features. The growth at 1900 °C/200 mbar results in AlN pattern consisting of individual single wurzite AlN crystallites with plate-like shape aligned along [ 1 1 ¯ 0 0 ] direction. The only defects these AlN crystallites contain are threading dislocations, some of which are terminated by forming half-loops. Because of the uniform distribution of the crystallites and their high structural perfection, this AlN pattern could represent interest as a template for bulk AlN growth. Alternative growth approaches to AlN crystallite formation are possible resulting in variation of the final AlN pattern structure. From a viewpoint of obtaining continuous patterns, the more favorable growth conditions involve applying of increased extrinsic gas pressure, 700 mbar in our case.