Piezo-phototronic effect in InGaN/GaN semi-floating micro-disk LED arrays

With enhanced light output efficiencies, InGaN/GaN micro-disk LED has received intensive attentions recently. Combining isotropic and anisotropic dry etching processes, an innovative semi-floating InGaN/GaN micro-disk LED array is fabricated, which shows remarkable light intensity enhancement up to 150% compared to the broad-base LED. A systematic study of micro-spectrums and Poisson-Schrodinger coupling self-consistent calculation reveal that there is non-uniform residual stress distribution on the micro-disk LED. Along microdisk center to micro-disk edge, as the Si substrate is etched off, the in-plane tensile stress in the GaN layer reduces, while the compressive stress in InGaN layer increases gradually. This gradient stress distribution has caused a non-uniform piezo-phototonic effect in the micro-disk LED, which in turn results in a maximum wavelength shift of 16 meV for the light emitted along micro-disk center to micro-disk edge. This study not only opens research of flexo-optoelectronic effect, e.g. non-uniform piezo-phototonic effect, in complex micro/nano optoelectonic/electronic devices, but also provides important guidance for the significant enhancement of light emission efficiency in micro-disk LEDs.