InGaN/GaN Quantum Well Microcavities Formed by Laser Lift-Off and Plasma Etching

Photoluminescence measurements have been used to investigate InGaN/GaN quantum well microcavities formed between two dielectric Bragg reflectors. Both single and ten-period quantum wells emitting near 420 nm were studied. The structures were formed using a combination of MOCVD growth for the nitride layers, laser lift-off to remove the sapphire substrates and electron-beam evaporation to deposit the mirrors. Room temperature photoluminescence measurements have been used to investigate the cavity modes observed from both plasma etched and unetched microcavities, and half widths as low as 0.6 meV were observed. The cavity modes were visible as dips in measured reflectance spectra and as peaks in the PL. Comparison of the mode wavelengths with simulated reflectivity spectra has allowed the determination of the cavity thickness before and after etching; this has shown the etch-back step to have a degree of control (±5%) necessary for the later fabrication of resonant periodic gain structures.