Design parameters for lateral carrier confinement in quantum-dot lasers

Quantum-dot (QD) lasers have fallen short of their promise of ultralow threshold and high characteristic temperature. Here, we report that QDs show great promise for controlling lateral carrier leakage. While oxide apertures continue to enable improved performance in vertical cavity surface emitting lasers (VCSELs) by reducing optical losses and current spreading, lateral carrier losses remain uncontrolled. We investigate QD active material in which lateral diffusion is intentionally reduced. Cathodoluminescence results demonstrate reduced lateral diffusion in the material with which we expect >50% reduction in the threshold current for 1-μm-wide edge emitters or 5-μm-diam VCSELs. However, initial edge-emitter results demonstrated 10% reduction due to unintended current spreading and lasing from higher states.