Band-engineered germanium for CMOS-compatible light emission
Abstract/Contents
- Abstract
- Modern electronics has advanced at a tremendous pace over the course of the last half century due to transistor scaling. However, while scaling a complementary metal oxide semiconductor (CMOS) transistor to smaller dimensions increases speed and reduces power consumption, the opposite is true for scaling down the copper interconnects that link these transistors. CMOS-compatible on- and off-chip optical interconnects offer a promising solution to this new performance bottleneck and several key components such as waveguides, detectors and modulators have already been demonstrated. However, a practical silicon CMOS-compatible light source remains elusive. Germanium has been proposed as a laser gain material due to its inherent compatibility with CMOS technology, but this requires overcoming the limitations imposed by germanium's indirect bandgap. Several techniques had been proposed to overcome this limitation such as n-type doping and band engineering through tensile strain. However, there was limited information about how effective each of these two techniques would be. There was also no truly CMOS-compatible technique for engineering large tensile strains in germanium for optimal band engineering. In this work we present theoretical and experimental answers to these problems. We begin with a theoretical investigation of the relative merits of n-type doping and band engineering through tensile strain to determine which is more useful. We then show theoretically that while n-type doping is of limited benefit, using a large tensile strain can result in an efficient low-threshold germanium laser. From there we present new CMOS-compatible techniques for engineering large tensile strains in germanium. Firstly, we improve upon an existing microbridge technique to achieve up to 5.7% uniaxial tensile strain in germanium. This is the highest such strain ever reported and is sufficient to turn germanium into a direct bandgap semiconductor. Secondly, we present a completely new technique for engineering up to 1.1% biaxial strain in germanium microdisks. This is the largest CMOS-compatible biaxial strain ever reported in germanium, and we further demonstrate an optical cavity integrated with our biaxially strained germanium structure. Finally, we discuss the implications of these theoretical and experimental achievements toward creating an efficient low-threshold germanium laser for use in CMOS-compatible on-chip light emission.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2015 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Sukhdeo, Devanand Suresh |
|---|---|
| Associated with | Stanford University, Department of Electrical Engineering. |
| Primary advisor | Saraswat, Krishna |
| Thesis advisor | Saraswat, Krishna |
| Thesis advisor | Harris, J. S. (James Stewart), 1942- |
| Thesis advisor | Vuckovic, Jelena |
| Advisor | Harris, J. S. (James Stewart), 1942- |
| Advisor | Vuckovic, Jelena |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Devanand Suresh Sukhdeo. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2015. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2015 by Devanand Suresh Sukhdeo
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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