Randomness dependence and generation mechanism of stimulated emission in regularly arranged InGaN/GaN nanocolumns

We report the dependence of randomness in sample configuration on stimulated emission phenomena in two-dimensional nanocolumn arrays. From the wavelength selectivity of the photoluminescence, we found that the stimulated emission is apparently related to a distributed feedback mechanism. By comparing the emission behavior between two regularly arranged InGaN/GaN nanocolumn samples with different degrees of randomness, we found that localization effects become prominent if the sample array has any randomness, even in an almost perfect sample. Several modes are localized at different areas in the nanostructures and partially overlap in space, and they compete with each other, especially in a slightly imperfect sample. In addition to the randomness dependence, by observing the wave number space images of the photoluminescence, we confirmed that the stimulated emission phenomena in the crystal arrays are generated by Bragg diffraction at photonic band edges, though the modes have some degree of variability via the sample randomness. (C) 2017 The Japan Society of Applied Physics