Publisher: Stanford University
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. The quantum-confined Stark effect in Ge/SiGe quantum well system paves the way to realize efficient optical modulation on Si in a fully CMOS compatible fashion. In this dissertation, we investigate the integration of Ge/SiGe quantum well waveguide modulators with silicon-on-insulator waveguides. For the first time, we demonstrate the selective epitaxial growth of Ge/SiGe quantum well structures on patterned Si substrates. The selective epitaxy exhibits perfect selectivity and minimal pattern sensitivity. Compared to their counterparts made using 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. A 3 dB optical modulation bandwidth of 2.8 THz is measured, covering more than half of the C-band. We propose, analyze, and experimentally demonstrate a novel approach to realize butt coupling between a SOI waveguide and a selectively grown Ge/SiGe quantum well waveguide modulator using a thin dielectric spacer. Through numerical simulation, we show that the insertion loss penalty for a thin 20 nm thick spacer can be as low as 0.13 dB. Such a quantum well waveguide modulator with a footprint of 8 [Mu]m2 has also been fabricated, demonstrating 3.2 dB modulation contrast with merely 1V swing at a speed of 16 Gpbs.