Perspectives on Advances in Quantum Dot Lasers and Integration with Si Photonic Integrated Circuits

Epitaxially grown quantum dot (QD) lasers are emerging as an economical approach to obtain on-chip light sources. Thanks to the three-dimensional confinement of carriers, QDs show greatly improved tolerance to defects and promise other advantages such as low transparency current density, high temperature operation, isolator-free operation, and enhanced four-wave-mixing. These material properties distinguish them from traditional III-V/Si quantum wells (QWs) and have spawned intense interest to explore a full set of photonic integration using epitaxial growth technology. We present here a summary of the most recent developments of QD lasers grown on a CMOS-compatible (001) Si substrate, with a focus on breakthroughs in long lifetime at elevated temperatures. Threading dislocations are significantly reduced to the level of 1 × 106cm-2via a novel asymmetric step-graded filter. Misfit dislocations are efficiently blocked from the QD region through well-engineered trapping layers. A record-breaking extrapolated lifetime of more than 200000 hours has been achieved at 80 °C, forecasting that device reliability is now entering the realm of commercial relevance and a monolithically integrated light source is finally on the horizon.