Preparation of a Freestanding AlN Substrate by Hydride Vapor Phase Epitaxy at 1230 °C Using (111)Si as a Starting Substrate

A freestanding (0001)AlN substrate with a thickness of 112 µm was successfully prepared by hydride vapor phase epitaxy (HVPE) of AlN at 1230 °C on a (111)Si starting substrate and subsequent removal of the Si substrate using a chemical etchant. The AlN substrate was transparent and displayed a smooth surface without cracks. Plan-view transmission electron microscopy (TEM) observations at the top surface of the AlN substrate revealed that an average dislocation density of 3 ×109 cm-2 was achieved. The dislocations were found to run inclined from the direction of growth. The AlN substrate exhibited a near-band-edge emission at 209.4 nm in the room-temperature photoluminescence spectrum.