Fabrication of high-quality nitride semiconductors by facet control technique

Abstract

Facet control during the growth of nitride semiconductors is a promising technique for obtaining a high-quality epitaxial GaN layer with low threading dislocation (TD) density. We have reported that facet-controlled epitaxial lateral overgrowth (FACELO) by metalorganic vapor phase epitaxy (MOVPE) for growth of GaN on a sapphire is a useful technique for reducing TD density and enables us to achieve TD densities on the order of 10⁶ cm^-2. AlGaN with high AlN molar fraction and low dislocation density is necessary for fabricating deep-UV emitters and detectors. A reduction in the TD density of AlGaN over the entire area of a surface was achieved by low-pressure MOVPE using a textured epitaxial AlN substrate. The AlN molar fraction of crack-free AlGaN is 0.51, and the TD density is estimated to be 8.8×10⁷cm^-2 from CL measurement, which is two orders of magnitude lower than that of AlGaN grown on a flat AlN epitaxial layer.