Defect structure of high temperature hydride vapor phase epitaxy–grown epitaxial (0 0 0 1) AlN/sapphire using growth mode modification process

Abstract

Defect structures were investigated by transmission electron microscopy for AlN/sapphire (0001) epilayers grown by high temperature hydride vapor phase epitaxy using a growth mode modification process. The defect structures, including threading dislocations, inversion domains, and voids, were analyzed by diffraction contrast, high-resolution imaging, and convergent beam diffraction. AlN film growth was initiated at 1450°C with high V/III ratio for 8min. This was followed by low V/III ratio growth for 12min. The near-interfacial region shows a high density of threading dislocations and inversion domains. Most of these dislocations have Burgers vector b=1/3〈1120〉 and were reduced with the formation of dislocation loops. In the middle range 400nm<h<2μm, dislocations gradually aggregated and reduced to ∼109cm−2. The inversion domains have a shuttle-like shape with staggered boundaries that deviate by ∼±5° from the c axis.Above 2μm thickness, the film consists of isolated threading dislocations with a total density of 8×108cm−2. Most of threading dislocations are either pure edge or mixed dislocations. The threading dislocation reduction in these films is associated with dislocation loops formation and dislocation aggregation-interaction during island growth with high V/III ratio.