The various arguments for introducing optical interconnections to silicon CMOS chips are summarized, and the challenges for optical, optoelectronic, and integration technologies are discussed. Optics could solve many physical problems of interconnects, including precise clock distribution, system synchronization (allowing larger synchronous zones, both on-chip and between chips), bandwidth and density of long interconnections, and reduction of power dissipation. Optics may relieve a broad range of design problems, such as crosstalk, voltage isolation, wave reflection, impedance matching, and pin inductance. It may allow continued scaling of existing architectures and enable novel highly interconnected or high-bandwidth architectures. No physical breakthrough is required to implement dense optical interconnects to silicon chips, though substantial technological work remains. Cost is a significant barrier to practical introduction, though revolutionary approaches exist that might achieve economies of scale. An Appendix analyzes scaling of on-chip global electrical interconnects, including line inductance and the skin effect, both of which impose significant additional constraints on future interconnects. Keywords—Off-chip wiring, on-chip wiring, optical interconnects, quantum-well modulator, vertical-cavity surface-emitting laser. I.

Abstract — We examine the current performance and future demands of interconnects to and on silicon chips. We compare electrical and optical interconnects and project the requirements for optoelectronic and optical devices if optics is to solve the major problems of interconnects to future high performance silicon chips. Optics has potential benefits in interconnect density, energy and timing. The necessity of low interconnect energy imposes low limits especially on the energy of the optical output devices, with a ~ 10 fJ/bit device energy target emerging. Some optical modulators and radical laser approaches may meet this requirement. Low (e.g., a few fF or less) photodetector capacitance is important. Very compact wavelength splitters are essential for connecting the information to fibers. Dense waveguides are necessary on-chip or on boards for guided wave optical approaches, especially if very high clock rates or dense WDM are to be avoided. Free space optics potentially can handle the necessary bandwidths even without fast clocks or WDM. With such technology, however, optics may enable the continued scaling of interconnect capacity required by future chips. Index Terms—ITRS roadmap, optical interconnections, optical modulators O I.

...................................................................................................................................... viii List of publications .......................................................................................................................ix Chapter 1: Introduction..................................................................................................................1 1.1 Scope and overall research contribution..............................................................................1 1.2 Motivation............................................................................................................................2 1.2.1 The interconnect problem .............................................................................................2 1.2.2 Capabilities and limitations of electrical interconnects................................................4 1.2.3 Advantages of optical interconnects ......................................

Abstract—We present observations of quantum confinement and quantum-confined Stark effect (QCSE) electroabsorption in Ge quantum wells with SiGe barriers grown on Si substrates, in good agreement with theoretical calculations. Though Ge is an indirect gap semiconductor, the resulting effects are at least as clear and strong as seen in typical III–V quantum well structures at similar wavelengths. We also demonstrate that the effect can be seen over the C-band around 1.55-µm wavelength in structures heated to 90 ◦C, similar to the operating temperature of silicon electronic chips. The physics of the effects are discussed, including the effects of strain, electron and hole confinement, and exciton binding, and the reasons why the effects should be observable at all in such an indirect gap material. This effect is very promising for practical high-speed, low-power optical modulators fabricated compatible with mainstream silicon electronic integrated circuits. Index Terms—Electroabsorption effect, germanium, optical interconnections, optical modulators, quantum-confined Stark effect (QCSE), silicon. I.

A senior colleague once told me that to finish a doctorate, one not only require being very hardworking, but also extremely patient. He didn’t mention about any intellectual abilities though. At the end of this long journey, I understood what he exactly meant. During my Ph.D. studies, I went through lots of academic and mental ups and downs. I want to thank everybody who supported me in any aspect during this period. First and foremost, I thank my parents, my Aai-Baba, who always seemed to be very close to me, even though they were thousands of miles away in India. I thank them for their unconditional love and faith in me. I also thank my brothers, Ajay and Vijay dada, and my sister-in-laws, Mrinal and Anjali Vahini, for supporting me throughout this period. There wasn’t a single day passed when I didn’t remember Aboli, Ashay and Aswin, the adorable kids in the family. It was extremely difficult to stay away from such a loving family, and very frustrating not to be able to meet them very often. But my friends made the stay not only easier, but a memorable one. I thank Laxmikant, Sunil, Amol, Naveen and Nagesh for a such a nice time. With them, it was like a home away from home. I would treasure all the happy