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Using periodically grooved substrates, we propose a new approach to the growth of low-dislocation-density GaN single crystal. Three different substrates of basal-plane sapphire, 6H-SiC(0001) Si and Si (111) were used. Each substrate's surface geometry was formed as periodical straight trenches oriented in either the 1100 GaN or 1120 GaN direction. No selective-growth mask of dielectric or metallic materials was deposited on any part of the substrates during the growth. The laterally grown area had etch pit densities of 4 × 10 6 cm −2 or less.

The critical amount of nitrogen atoms at the interface, above which the roughness of the oxynitride/Si(100) interface increases, was studied using noncontact-mode atomic force microscopy and X-ray photoelectron spectroscopy. The interface roughness was found to increase upon increasing the amount of nitrogen atoms at and near the interface if the amount of nitrogen atoms is greater than 0.37 monolayers. This increase in interface roughness was found to be reflected in an increase in surface roughness of almost the same amount.

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