Ultra-low threshold green InGaN quantum dot microdisk lasers grown on silicon

Abstract

We report ultra-low threshold green InGaN quantum-dot (QD) microdisk lasers directly grown on Si substrates by metal-organic chemical vapor deposition. Vertically stacked InGaN/GaN QDs by epitaxy on Si were adopted as the microcavity gain medium. Under continuous-wave optical pumping, we observed room temperature lasing at 522 nm from the microcavity lasers with a diameter of 1.0 μm and obtained an ultra-low threshold of 76 W/cm2. The sidewall roughness values of the microdisk lasers etched by different solutions of potassium hydroxide and HF/HNO3 were compared. We detected a strong correlation between the lasing thresholds and the sidewall roughness of the microdisk lasers, with the lasing threshold improved from 1.6 kW/cm2 to below 100 W/cm2 and the full width at half maximum reduced from 0.53 nm to 0.2 nm through smoothing of the sidewall.