Strain Relaxation Characteristics of a Single InGaN-based Nanopillar Fabricated by Focused Ion Beam Milling

摘要

A free-standing nanopillar with a diameter of 300 nm, and a height of 2 μm is successfully demonstrated by focused ion beam milling. The measured micro-photoluminescence (μ-PL) from the embedded InGaN/GaN multiple quantum wells shows a blue shift of 68 meV in energy with a broadened full-width at half maximum, ～200meV. Calculations based on the valence force field method suggest that the spatial variation of the strain tensors in the nanopillar results in the observed energy shift and spectrum broadening. Moreover, the power-dependent μ-PL measurement confirms that the strain-relaxed emission region of the nanopillar exhibits a higher radiative recombination rate than that of the as-grown structure, indicating great potential for realizing high-efficiency nano devices in the UV/blue wavelength range.