Lateral carrier localization in quantum dot lasers

Quantum dot lasers so far have fallen short of their initial promise of ultra-low threshold and extremely high characteristic temperature due to unavoidable dot size variation. Here we report that QDs show great promise for controlling lateral carrier leakage despite such size distribution. While oxide-defined apertures continue to demonstrate improved performance in semiconductor lasers by reducing optical losses and current spreading, lateral carrier losses remain uncontrolled. We have investigated self-assembled quantum dot active material in which lateral diffusion is intentionally reduced. Cathodoluminescence (CL) results demonstrate significantly reduced lateral diffusion in the materials with which we expect 50% reduction in the threshold current. However, initial device results using these materials reveal that ground state lasing is necessary to realize the expected reduction in the threshold current, and if lasing is supported by a higher state with lower confinement energy, the reduction in lateral diffusion is not realized