Pulsed lateral epitaxial overgrowth of aluminum nitride on sapphire substrates

Abstract

The authors report on pulsed lateral epitaxial overgrowth of aluminum nitride films on basal plane sapphire substrates. This approach, at temperatures in excess of 1150°C, enhanced the adatom migration, thereby significantly increasing the lateral growth rates. This enabled a full coalescence in wing regions as wide as 4–10μm. Atomic force microscopy and cross-section transmission electron microscopy were used to establish the reduction of threading dislocations in the lateral growth. Cross-sectional monochromatic cathodoluminescence and photoluminescence measurements confirmed the improved optical properties of the laterally overgrown aluminum nitride films.

Temperature dependence of the crystalline quality of AlN layer grown on sapphire substrates by metalorganic chemical vapor deposition

“…One of the common approaches to reducing the dislocation density is epitaxial lateral overgrowth (ELO) where AlN layers are re-grown on patterned seeding AlN templates [4][5][6][7]. However, because the ELO approach involves cleanroom fabrication like lithography and etching as well as a regrowth process of the several μm thick layer to coalesce and form a flat layer over the patterned templates, it is associated with much more additional cost and processing time, uneven surfaces, and growth complexity.…”

High‐temperature growth of AlN in a production scale 11 × 2′ MOVPE reactor

“…Two main approaches are followed to improve the quality of epitaxially grown AlN. First, the method of migration-enhanced epitaxy or pulsed growth is proposed to enhance surface mobility of adsorbed atoms [2]. Second, high-temperature growth is facilitated to improve surface diffusion length of Al [3].…”

Influence of the growth temperature of AlN buffer on the quality and stress of GaN films grown on 6H–SiC substrate by MOVPE

“…That means the AlN buffer layer grown at 1100 • C gives GaN epilayer greater compressive strain. It can be explained as follows: if AlN film was grown at a lower temperature, the atom diffusion length would be decreased, leading to a three-dimension growth mode, the coalescence of the nuclear island may not occur [24,36]. Therefore, the compressive stress in GaN film generated by a lower growth temperature AlN buffer is not large enough to compensate the tensile stress which is brought by the cooling down process.…”