Silicon and Epitaxially Grown III-V-On-Silicon Photonic Devices for On-Chip Optical Interconnects

On-chip optical interconnects is one promising technology to replace conventional electrical interconnects for large-data-capacity and low-power-consumption communications on integrated circuit (IC) chips. Among various nascent technology platforms for optical interconnects, silicon photonics leveraging the mature silicon nanoelectronics fabrication processes offers the key advantage of a potentially manufacturable integration of optical interconnects on silicon IC chips.;In this thesis, we propose and demonstrate a number of functional silicon photonic devices for on-chip optical interconnect applications including (i) electro-optical tunable delay lines, (ii) photocurrent monitors for silicon microresonator-based switches and modulators and (iii) epitaxially grown III-V-on-silicon photodetectors.;Silicon tunable time delay lines are key components for optical networks. We demonstrate electro-optical tunable time delay and advance using silicon feedback-microring microresonators integrated with p-i-n diodes. By controlling the feedback and round-trip phase shifts through the carrier injection-based free-carrier dispersion effect, we obtain a large dynamic time tuning range (--88 ps to 110 ps) upon dc bias voltage change in the range of few tens of millivolts at a given resonance wavelength. We also demonstrate tunable time delay and advance at different resonance wavelengths within 0.76nm wavelength range.;Silicon microresonators also act as essential building blocks in the form of filters, switches and modulators for on-chip optical interconnects. However, the resonance wavelengths of silicon microresonators are susceptible to optical carrier wavelength drift and environmental temperature variation. An adaptive feedback-based solution to actively stabilize the resonance wavelength is desirable. To this end, we propose to use on-chip all-silicon photodetectors to monitor the resonance wavelengths of silicon microresonators. We study the on-chip all-silicon photodetectors employing sub-bandgap surface-state absorption and two-photon absorption induced photocarrier generation. We integrate the photodetectors with silicon microresonators in order to monitor the spectral alignment between the optical carrier wavelength and the resonance. We demonstrate real-time in-microresonator photocurrent monitoring for silicon microring carrier-injection switches. We also demonstrate real-time in-microresonator photocurrent monitoring for silicon feedback-microring carrier-injection modulators.;Given that silicon is essentially transparent in the 1300-1550nm telecommunications wavelengths, it constitutes a low-loss material for integrated waveguides in the telecommunications window but not an efficient photodetector. One way to enable photodetection on silicon chips in the telecommunications wavelengths is to hybrid-integrate III-V semiconductor photodetectors on silicon chips. On this front, we develop epitaxially grown III-V-on-silicon normal-incidence and silicon waveguide butt-coupled photodetectors by metalorganic chemical vapor deposition (MOCVD). The waveguide butt-coupled device with a 20mum x 20mum area shows a dark current of 2.5 muA and a responsivity of 0.17 A/W at 1550nm wavelength upon -1V bias voltage, a 3dB bandwidth of 9 GHz upon -4V bias voltage and an open eye diagram at 10Gb/s data rate upon -4V bias voltage. The photodetectors show promising performances for on-chip optical interconnects applications. The developed epitaxial III-V-on-silicon technology with silicon waveguide integration can be naturally extended into integration with more sophisticated silicon photonic devices.