Direct epitaxial integration of III-V optoelectronic devices on Si offers a substantial manufacturing cost and scalability advantage over heterogeneous integration via wafer bonding. The challenge in utilizing direct epitaxy of III-Vs on Si is that epitaxial growth introduces high densities of crystalline defects that limit device performance and lifetime. As an optical gain medium, quantum dots exhibit a unique tolerance to crystalline defects due to their three-dimensional quantum confined structure.
Quantum dot lasers epitaxially grown on Si are showing promise for achieving low-cost, scalable integration with silicon photonics. Their atom-like, inhomogeneously broadened, discrete density of states yields unique gain properties that show promise for improved performance and new functionalities relative to their quantum well counterparts (even on native substrates). By reducing the dislocation density in III-V/Si material and improving quantum dot size homogeneity, several world record results have been achieved for epitaxial laser performance on silicon.
A subset of the results achieved include continuous-wave threshold currents below 1 mA in micro-scale ring laser cavities, single-facet output powers of 175 mW at 20 °C, continuous wave lasing up to 105°C, near zero linewidth enhancement factor, isolator-free stability at optical feedback levels of up to 90%, and record long device lifetimes on silicon of more than 100 years at 35°C based on extrapolated 8,000-hour aging studies, and >100,000 h lifetimes at 60°C from extrapolated 4,000-hour aging studies. These results show potential to revolutionize integrated photonics through economic advantages and performance capabilities not achievable in quantum well lasers.