TECHNOLOGY INTEGRATION
wider the opening in SiO2
, the better the thermal conductivity,
so we have tried to use this in our templates. This has led us to optimise the deposition process for structures with 1 μm-wide openings in SiO2
By optimising our growth process, we can realise complete defect fi ltering with these processed wafers, while maintaining a smooth SiO2
new defects.
Getting the light in Integration of III-Vs and silicon requires coupling of the generated optical mode in the active region to the underlying silicon. To do this, there must be evanescent coupling of the optical mode with the silicon waveguide, which is buried in the dielectric mask in such a way that the whole structure works not only as a defect fi lter but also as a platform for evanescent coupling of the optical mode.
Simulations by us, and also by the group of Pallab Bhattacharya from the University of Michigan, show that evanescent coupling can occur between InGaAs/GaAs based quantum dot lasers and a lab-grown silicon-SiO2
waveguide-cladding structure with
similar dimensions. We are still to fabricate fi nal devices using our ELOG technology. However, we don’t anticipate any major
Figure 6. Transmission electron microscopy shows the high quality of the InGaAsP multi-quantum wells grown on uncoalesced ELOG InP on silicon.
obstacles to realising this, given the excellent material quality of the isolated large areas of InP, and the subsequent growth of uniform InGaAsP multiple-quantum wells.
One of the challenges that still lies ahead is that the photonic industries continues to live in the micro world, and substantial scaling is therefore required, given that the electronics industry has reached the smallest possible nano-dimensions.
Other groups have started to try and close this gap by either developing tiny plasmonic-based devices or ultra-small cavity lasers based on GaAs nanowires and InP polytypic nanorods – the latter feature ultra-low thresholds.
Our integration scheme may help in all these efforts, because it promises to deliver an affordable, monolithically integrated platform for III-Vs and silicon that can form the foundation for the highly complex photonic integrated circuits needed in the near future.
Figure 5. Cross-sectional transmission electron microscopy reveals the defect-fi ltering mechanism in wide openings.
Several co-workers in our laboratory contributed to this work. This work was partially supported by URO of Intel Inc., US, in which we enjoyed the fruitful collaboration with John Bowers from UCSB.
that are etched to a depth of 2 μm. surface and sidewalls to avoid generation of any
Further reading H. Kataria et. al. Semicond. Sci. Technol. 28 094008 (2013) H. Kataria et. al. IEEE J. Sel. Top. Quant. Electron. 20 JULY/AUGUST (2014) H. Kataria et. al. Proc. of SPIE 8989 898904-1. Z. Wang et. al.. Materials Science and Engineering B 177 1551 (2012) J. Wang et. al. Opt Exp. 16 5136 (2008)
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