Three-dimensional GaN templates for molecular beam epitaxy of nonpolar InGaN/GaN coaxial light-emitting diodes

Abstract

This work highlights the development of three-dimensional (3D) GaN templates grown by metal organic vapor phase epitaxy (MOVPE). These templates are ideally suited for the subsequent growth of nonpolar (11¯00) m-plane InGaN-based coaxial wire/wall light-emitting diodes (LEDs) using molecular beam epitaxy (MBE). The use of MBE is expected to result in increased indium incorporation on the (11¯00) m-plane, compared with growth using MOVPE, which provides an attractive approach for the development of nonpolar green LEDs. While planar free-standing m-plane GaN substrates are prohibitively expensive (approximately ∼$500 per cm2), the coaxial LED approach offers an attractive lower-cost alternative. These nonpolar nanoscale LED templates are also free from threading dislocations and are expected to provide a number of benefits, including higher light extraction and a larger effective active region area. Previous work in our group has demonstrated the controlled growth of GaN nanowires using a catalyst-free selective-area MOVPE growth method. The present work extends this method to grow 3D GaN templates in various aperture geometries, resulting in smooth m-plane GaN using a scalable and industrially viable high-quality GaN growth technique. In addition to m-plane sidewalls, the authors also demonstrate semipolar (11¯01) inclined sidewalls. This orientation has been shown to incorporate indium at a higher rate during MOVPE growth, in comparison to both c-plane and m-plane.