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Two-dimensional (2D) light diffraction in a uniform array of GaN nanocolumns arranged in a rectangular lattice dramatically enhanced the light intensity at a specific wavelength, indicating the function of 2D distributed feedback (DFB). Here a GaN rectangular-lattice nanocolumn array, which integrated InGaN/GaN multiple quantum wells (MQWs) in the top region of the nanocolumns, was grown by rf-plasma-assisted molecular beam epitaxy (rf-MBE). At a specific wavelength of 471.1 nm, the first observation of stimulated emission from 2D-DFB in an InGaN-based nanocolumn array was obtained. The specific wavelength is calculated by the 2D finite-difference time domain (2D-FDTD) method on the assumption of a refractive index dispersion of GaN; a simple expression for specific wavelength, which is a function of the array period L and the hexagon side length S of each nanocolumn, is proposed, which is convenient for producing a simple design of a GaN nanocolumn array structure in a square lattice.

Hexagonal boron nitride (h-BN) films were grown on c-plane sapphire substrates by low-pressure chemical vapor deposition with BCl3 and NH3 as the boron and nitrogen sources, respectively, and the influences of growth parameters on the film quality were investigated for samples with a thickness of about 1 µm. The dependence of X-ray diffraction on the growth temperature (T g) indicated that the crystalline quality is most improved in the sample grown at 1200 °C, in which the epitaxial relationship of {100}h-BN ∥ {110}sapphire and {001}h-BN ∥ {001}sapphire was confirmed. This condition enhanced lateral growth, resulting in the formation of grains with flat top surfaces. The T g dependence was discussed in relation to the amorphous AlN formed on the substrate surface and the reaction between BCl3 and NH3 in the vapor phase. The correlation between the structural and luminescent properties, which was found from the T g dependence of CL, was also discussed.

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