Study of epitaxial lateral overgrowth of GaN for application in the fabrication of optoelectronic devices

Abstract

In this research effort, epitaxial lateral overgrowth (ELOG) of GaN on sapphire was performed by low-pressure metalorganic chemical vapor deposition (MOCVD) in a horizontal reactor. All ELOG growths were stopped prior to complete coalescence, and the resulting cross-sections were characterized by scanning electron microscopy (SEM). Both vertical {1120} and inclined sidewalls were observed. Inclined {112 n }sidewalls of various angles (n ≈ 2-2.2) were found as previously reported in the literature 1 . Both one-step and two-step ELOG processes were used to control the overgrowth geometry. It was confirmed that sidewall formation and growth rates are closely correlated with multiple parameters including temperature and V/III ratio 1 . It was also found that substrate rotation greatly influences sidewall evolution and vertical growth rate. A conceptual model was begun to completely describe the ELOG process in a horizontal reactor. It is speculated that the different sidewalls observed as a function of substrate orientation result from variation in the local V/III ratio. Once developed, the final model will be used to control the sidewalls in the growth of ELOG structures for the fabrication of novel optoelectronic devices.