Stanford University PhD Oral Defense – Department of Electrical Engineering
Ph.D. Candidate: Shen Ren
Advisor: Prof. David. A. B. Miller
Date: Monday, Dec 13th, 2010
Time: 10am (Refreshments start at 9:45am)
Location: CISX Auditorium (101X)
Title: Ge/SiGe Quantum Well Waveguide Modulator for Optical Interconnect Systems
Abstract
Thanks to the development of silicon VLSI technology over the past several decades, we can now integrate far more transistors onto a single chip than ever before. However, this also imposes more stringent requirements, in terms of bandwidth, density, and power consumption, on the interconnect systems that link transistors. The interconnect system is currently one of the major hurdles for the further advancement of the electronic technology. Optical interconnect is considered a promising solution to overcome the interconnect bottleneck.
In this presentation, I will first briefly introduce the optical interconnect system. Then a special type of device in the optical interconnect system, the optical waveguide modulator that is based on Ge/SiGe quantum well (QW) structures, will be presented. Such QW structures can be grown monolithically on silicon substrates in a fully CMOS compatible fashion. For the first time, we demonstrated the selective epitaxial growth of these structures on patterned substrates. The selective epitaxy exhibits minimal pattern sensitivity under optimized growth conditions. Compared to its counterparts through bulk epitaxy, the p-i-n diodes from selective epitaxy demonstrate very low reverse leakage current and high reverse breakdown voltage. Strong quantum-confined Stark effect (QCSE) is, for the first time, demonstrated in this material system in the telecommunication C-band at room temperature. Then I will present our approach of integrating the Ge/SiGe QW active optical modulators into the silicon-on-insulator (SOI) waveguide platform through selective epitaxial growth. We proposed, analyzed, and experimentally demonstrated a novel approach to realize the butt coupling between SOI waveguide and Ge QW waveguide modulator using a thin dielectric spacer. 3.2dB modulation contrast ratio is achieved with merely 1V dynamic swing. We also show high speed modulation up to 3.5GHz, which is currently limited by our testing capability.
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Best wishes,Shen Ren Department of Electrical EngineeringStanford University The optimist thinks this is the best of all possible worlds. The pessimist fears it is true. - Robert Oppenheimer