Influence of an in situ-deposited [formula omitted] intermediate layer inside GaN and AlGaN layers on SiC substrates

Abstract

In this work we present a study on the influence of an in situ grown SiN x intermediate layer inside (Al)GaN epitaxial layers grown on SiC substrates on dislocation densities and material strain of the epitaxial films. A defect density of 6 × 10 8 cm - 2 was achieved by reducing the number of pure edge dislocations in the order of one magnitude. It was found that a reduction of the dislocation density is only successful by inserting the SiN x layer inside GaN films and no defect reduction takes place with SiN x inside AlGaN films. The presence of stacking faults at the close vicinity of the SiN x layer plays an important role for the mechanism of dislocation termination at the SiN x interface. To determine dislocation densities an etch pit density method was carried out combining transmission electron microscopy (TEM) investigations of plan-view samples with atomic force microscopy (AFM) scans. Structural properties were investigated by cross-sectional TEM samples. Composition of AlGaN at the SiN x interface was determined by energy dispersive X-ray analysis (EDX) and secondary ion mass spectroscopy (SIMS). Material strain was investigated by micro-photoluminescence measurements ( μ -PL).