Departmental Seminar

Epitaxially-grown III-V micro-ring lasers for Si photonics applications

Mr Wei Wen Wong
ANU

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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.

In the first part of the talk, I will present results of epitaxially-grown InP micro-ring lasers, which include the cavity design and modelling, growth process, and lasing characteristics. With the optimised cavity design and growth conditions, the micro-ring lasers, as-grown on InP substrate, operate at room-temperature with a low lasing threshold. 

Next, in the second part of the talk, I will discuss the progress made so far in terms of growing InP micro-ring lasers on Si substrate. To demonstrate the potential of the micro-ring laser as an integrated light source for Si photonics, growth on Si substrate is crucial. 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. The effect of various growth conditions such as growth temperature and precursor flow rates on the surface morphology of the nucleation layer will be discussed. Finally, I will present future plans of developing the growth process on Si substrate, in particular optimising the in-situ annealing step to minimise the surface roughness of the nucleation layer. 

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