Temperature dependence of a‐plane GaN low angle incidence microchannel epitaxy by ammonia‐based metal‐organic molecular beam epitaxy

Abstract

The growth temperature dependence of a‐plane GaN produced by low angle incidence microchannel epitaxy using NH3‐based metal‐organic molecular beam epitaxy was studied. It was found that the width of the laterally grown region increased with temperature. This was because at low temperatures, {10‐12} side facets were formed, which suppressed the lateral growth process by giving rise to inter‐surface diffusion of Ga adatoms from the side to the top of the growing layer. These facets also caused the lateral growth front to assume a zigzag shape. The formation mechanism of the facets can be understood in terms of the Mullin‐Sekerka instability, by which minute periodic undulations gradually increase with growth time when their period is larger than a certain critical value, which increases with growth temperature. Defects in the epitaxial layers were also studied using transmission electron microscopy. Although the defect density was found to be very low in the laterally grown layer itself, a very large number of dislocations and stacking faults were observed both in the template layer and in the epitaxial regions above the openings. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of Supply Direction of Precursors on a-Plane GaN Low Angle Incidence Microchannel Epitaxy by Ammonia-Based Metal–Organic Molecular Beam Epitaxy

“…These facets are thought to be formed as a result of growth instability. 9) Therefore, a certain extent of lateral growth is possible before the entire side is covered by facets. After the formation of facets, adatoms are thought to migrate from the side to the top and, consequently, a thick layer is grown near the side.…”

“…7) The temperature and [NH 3 ]/[TMG] (TMG: trimethylgallium) flow rate dependences of a-plane GaN LAIMCE have been studied to optimize the growth conditions for obtaining a wide lateral overgrowth. 8,9) The crystal direction of the microchannel is another important factor for controlling lateral growth because it largely affects facet formation on the sides. Therefore, in the present study, the effects of the direction of precursor supply were investigated.…”