Gallium Nitride Crystals Grown by Hydride Vapor Phase Epitaxy with Dislocation Reduction Mechanism

Abstract

The growth of high-crystalline-quality GaN by hydride vapor phase epitaxy, focusing on dislocation density reduction, was studied, and a facet-initiated epitaxial lateral overgrowth (FIELO) method has been proposed. In this method, a GaN layer develops by the overgrowth of facet structures generated from narrow channels opened in a SiO2 mask formed on a GaN template. The threading dislocations changed their propagation direction, bending in the horizontal direction, due to the facet structure. To reduce the number of threading dislocations through the channels, we propose a novel FIELO method with nanometer-size channels. The dislocation density was found to decrease to 4.5 x 10(7) cm(-2) for a 20-mu m-thick GaN layer. We also developed random-island FIELO, in which micrometer-size small islands are initially formed on a TiC buffer layer by low-temperature growth of GaN on a sapphire substrate. Under higher growth temperatures that follow, the growth of these small islands changes to three-dimensional (3D) growth with facet planes. The 3D growth was maintained for a thickness of approximately 100-200 mu m. As a result, the dislocation density was reduced to similar to 3 x 10(6) cm(-2). Freestanding 2- and 4-inch-diameter GaN substrates were also successfully fabricated by using the random-island FIELO method. (C) 2013 The Electrochemical Society. All rights reserved.