As miniaturization of the semiconductor technology node continues to follow the timeline defined by the International Technology Roadmap for Semiconductors, bottlenecks have begun to arise at the interconnect level. To overcome limitations facing electrical interconnects, optical interconnects have been proposed for on-chip and off-chip communication bandwidth to properly scale with processing speed. Operating at optical frequencies permits much higher bandwidth than existing electrical approaches that rely on complex signal processing algorithms. However, successful implementation of optical interconnects requires active optoelectronic devices integrated onto silicon (Si), the foundation of modern electronics. Such devices include lasers as well as photodetectors. Making such devices compatible with silicon processing technology is economically necessary given the massive silicon infrastructure that currently exists.
Monolithic integration of optically superior Group III-V materials onto silicon is a desirable approach to implement such devices since the indirect band gap of silicon makes it an extremely inefficient light emitter. However, such integration has been limited by large lattice mismatch preventing growth of high-quality Group III-V films on silicon. Another problem facing Group III-V optoelectronic devices on silicon is that silicon and Group III-V materials have highly similar refractive indices. This renders waveguiding and confinement of light in optically active Group III-V structures on silicon a difficult task that must be addressed. Lastly, optoelectronic devices at the nanoscale are of interest since electronic components have already reached nanoscale dimensions. Thus, it is also critical to find a proper means of strongly confining light in structures approaching or below the diffraction limit of light.
As such, there is a need for a monolithically integrated optical resonator that satisfies the aforementioned constraints, thereby paving the way, for instance, for on-chip and high density optoelectronic devices such as, but not limited to, lasers.