Stimulated emission on two-dimensional distributed feedback scheme in triangular GaN nanocolumn arrays

Triangular GaN nanocolumn arrays, in which InGaN/GaN multiple quantum wells were integrated at the top region of each nanocolumn, were grown by Ti-mask selective-area growth of RF-plasma-assisted molecular beam epitaxy. In the nanocolumn arrays, a strong enhancement in light intensity at the specific wavelength of 479.4 nm was observed under low optical excitation, and then optically pumped stimulated emission occurred at near the specific wavelength (476.3 nm) under high optical excitation with a threshold excitation density of 400 kW/cm². The light response of the nanocolumn array was numerically analysed by two-dimensional (2D) finite-difference time-domain and 2D plane-wave expansion methods, proving that the stimulated emission occurred in the 2D distributed feedback scheme.