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

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 H3PO4, 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 5×105 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 cm2/V s and about 4×1017 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.