Hydride vapour phase epitaxy growth and characterization of thick GaN using a vertical HVPE reactor

Abstract

Growth of 2-inch diameter bulk GaN layers with a thickness up to 2 mm is demonstrated in a vertical hydride vapour phase growth reactor. Morphology, dislocations, optical and electrical properties of the material have been investigated using atomic force microscopy, optical microscopy, decorative etching in hot H 3PO 4, Hall measurements and low-temperature photoluminescence. Atomic force microscopy reveals a two-dimensional step flow growth mode with step bunching for layers with a thickness of 250 μm. As the growth proceeds, the morphology is changed to a hill and valley structure. The EPD was determined to 5×10 5 cm −2 for a 2 mm thick layer. The Hall mobility and the carrier concentration were determined. For a 1.7 mm thick layer at 300 K the mobility and the carrier concentration is 520 cm 2/V s and about 4×10 17 cm −3, respectively. Low-temperature photoluminescence spectra measured on a 350 μm thick freestanding layer show the DBE line at 3.4707 eV with a full-width half-maximum of 1 meV, confirming a stress free GaN layer.