SiGeSn-based Quantum-Well Lasers and Electroabsorption Modulators
Date Issued
2010
Date
2010
Author(s)
Chang, Guo-En
Abstract
Compact electronic-photonic integrated circuits are one of the promising technology to enable on-chip, low-power, high-speed optical networks for telecommunications and inter/intra-chip interconnections. High-performance Si-based lasers and modulators are critical to achieve the goal: the former generate coherent light while the later optically encode light signals at the optical transmitter end. However, the light-emitting efficiency in Si is very low due to its indirect bandgap in nature, and fast modulation in Si is challenging because of the lack of efficient linear electro-optical and electroabsorption effects. Thus, high-performance electronic-photonic integrated circuits are not possible until the realization of electrically-pumped Si-based lasers and highspeed modulators. This dissertation focuses on the research of using novel SiGeSn material system for efficient Si-based electrical-pumped lasers and electroabsorption modulators.
SiGeSn material system represents a new promising platform to develop Si photonics. With the significant advances in the growth of SiGeSn material system by low-temperature UHV-CVD, high-quality GeSn, SiSn, and SiGeSn alloys are able to be grown. To explore possible electronic and photonic devices based on the novel SiGeSn material system, we first study the fundamental properties of Si, Ge, and α-Sn as well as their compounds, in cluding the electronic, optical, and mechanical properties.
Among the group-IV semiconductors, Ge is a potential material for efficient electrically-pumped Si-based lasers and high-speed modulators. Ge is a quasi direct-bandgap semiconductor, suggesting the possibility of transforming it into a direct bandgap semiconductor for photonic active applications. We propose two approaches to crate direct-bandgap semiconductors based on the SiGeSn material system for developing Si-based lasers: tensile-strained, n-type doped Ge/SiGeSn quantum wells, and strain-balanced GeSn/SiGeSn multiple-quantum-well. We develop a theoretical model for laser analysis, including the strained electronic band structure, carrier occupation, polarization-dependent optical gain, polarization-dependent optical confinement factor, and threshold analysis. Our calculations indicate lasing action in the two designed lasers is possible.
While Si has no linear electro-optical and very weak electroabsorption effects for efficient, high-speed modulators, Ge is suitable for Si-based modulators because it possesses significant Franz-Keldysh and quantum-confined Stark effects. We propose and analyze two structures for electroabsorption waveguide modulators operating at 1550 nm wavelength based on the quantumconfined Stark effect: tensile-strain Ge/SiGeSn quantum wells and strainfree GeSn/SiGeSn quantum wells. A theoretical model for describing the quantum-confined Stark effect is present. With adequate design of the quantumwell materials and waveguide geometry, it is possible to achieve effective modulation at 1550 nm wavelength using the two designed electroabsorption modulators for electronic-photonic integrated circuits.
Subjects
Si photonics
GeSn alloys
SiGeSn alloys
strained QW lasers
MQW electroabsorption modulators
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-99-F92543048-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):5c67812bf5e963e517ec26cbff7ad14a