Strain relaxation induced microphotoluminescence characteristics of a single InGaN-based nanopillar fabricated by focused ion beam milling

Abstract

A freestanding nanopillar with a diameter of 300nm and a height of 2μm is demonstrated by focused ion beam milling. The measured microphotoluminescence (μ-PL) from the embedded InGaN∕GaN multiple quantum wells shows a blueshift of 68meV 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 suggests that the strain-relaxed emission region exhibits a higher radiative recombination rate than that of the strained region, indicating potential for realizing high-efficiency nanodevices in the UV/blue wavelength range.