Epitaxially-grown III-V micro-ring lasers for Si photonics applications
Despite the significant progress in the research of III-V semiconductor nanowire lasers, integrating nanowire lasers on photonic devices has been shown to be technically-challenging. In this regard, III-V micro-disk and micro-ring lasers are excellent candidates for integrated miniature lasers, since the laser emission can be efficiently coupled to on-chip waveguides. However, since these types of lasers have been fabricated via top-down fabrication approaches, their performance is adversely affected by sidewall roughness induced by etching process. Moreover, the limited scalability of top-down fabrication approaches also hinders the realisation of high-density monolithic integration.
Recently, we have demonstrated whispering gallery mode lasing in epitaxially-grown InP micro-ring lasers at room-temperature. Due to the self-termination properties of low-energy crystallographic surfaces during growth, the side facets of these micro-rings are atomically-smooth and form excellent mirrors with very low losses. More importantly, epitaxial growth offers better scalability for monolithic integration compared to most top-down fabrication techniques.
The current focus of this project is to grow these micro-ring lasers on Si substrates to demonstrate their potential as integrated light sources for Si photonics. To accommodate the high defect density at the InP/Si interface, we have grown a low-temperature InP nucleation layer on Si (111) substrate with the atomic layer epitaxy (ALE) and flow-rate modulation epitaxy (FME) techniques. In future, we plan to further optimise the crystal quality of the nucleation layer and perform high-temperature micro-ring growth on the nucleation layer.