LOW-DISLOCATION-DENSITY GaN AND AlGaN USING EPITAXIAL-LATERAL-OVERGROWTH METHODS

摘要

The epitaxial-lateral-overgrowth (ELO) is one of the most important techniques to obtain low threading dislocation (TD) density in Ⅲ-nitride epitaxial layers. The TD density in GaN epilayers is dramatically reduced to the order of 10~6 cm~(-2) with good reproducibility by using the facet-controlled-epitaxial-lateral-overgrowth (FACELO) method in metal organic vapor phase epitaxy (MOVPE). Furthermore, crack-free and high-quality AlGaN with TD density of lower than 10~(10) cm~(-2) is successfully obtained by growing on an epitaxial AlN layer on (0001) sapphire substrate. The FACELO technique has been developed to reduce the low TD density in AlGaN epilayers grown by MOVPE. The new approach of growing low TD density Al_xGa_(1-x)N (x = 0.4-0.5) using AlN epilayer with inclined facets and rugged facets has been proposed. The TD density in the AlGaN epilayer is reduced to the order of 10~7 cm~(-2) from over 10~(10) cm~(-2).