Kyo-Yeol Lee

Properties of Freestanding GaN Substrates Grown by Hydride Vapor Phase Epitaxy

We report on freestanding GaN thick films with a thickness of 300 µm grown on 2-inch sapphire (0001) substrates by hydride vapor phase epitaxy. In order to improve the surface morphology of GaN with hillocks, we polished its surface with diamond abrasives and investigated the photoluminescence properties of the polished GaN. Transmission electron microscopy measurement was used to observe the subsurface damage layers. We used the dry etching method, chemically assisted ion-beam etching (CAIBE), for the removal of the damage layer and identified the recovery of photoluminescence properties. As a result, the morphology of the homoepitaxial GaN regrown layer was improved by ion-beam etching compared to that of the not-etched layer.

Properties of Etched Ga- and N-Faces of Freestanding GaN Substrate Using Inductively Coupled Plasma-Reactive Ion Etching

The dependence of the etch rate and surface roughness on the polarity of undoped GaN was investigated. A freestanding GaN substrate was etched using Cl2-based inductively coupled plasma-reactive ion etching (ICP-RIE). The etch rates of the N-face and Ga-face of freestanding GaN were ~ 10000 A/min and ~ 8000 A/min at 600 W, respectively. The dry-etched N-face of freestanding GaN has a rougher surface than the Ga-face. The photoluminescence intensity of near-band-edge transition in the N-face increased with increasing ICP source power, while that of the Ga-face slightly decreased. The etch rate and surface roughness of the N- and Ga-faces depend on the polarity of GaN.