Study of compound semiconductor quantum dots for photonic modulators

• Main Author: Ngo, Andrew Chun Yong.
• Other Authors: Yoon Soon Fatt
• Format: Theses and Dissertations
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Optics, optoelectronics, photonics
• Online Access: http://hdl.handle.net/10356/42315
• Institution: Nanyang Technological University

The demand of bandwidth capacity is rising exponentially in recent years due to the spread of high-speed Internet. For low-cost Metropolitan Area Network (WAN), operating wavelength at 1.3 µm is chosen. Conventionally, optoelectronic devices operating at 1.3 µm were based on InP substrates. GaAs is not chosen due to the absence of low bandgap material that, at the same time, can be lattice-matched to GaAs. This takes a turn in the mid-1980s when it was found that epitaxial growth of highly lattice-mismatched semiconductor heterostructures can lead to self-assembly of coherently strained and defect-free three-dimensional nano-islands, also known as quantum dots (QDs). Consequently, there exists a larger pool of epitaxial material on GaAs since the choice is no longer limited by the issue of lattice mismatch. Most importantly, optoelectronic devices operating at long wavelength can now be realized on GaAs substrates. The most extensively studied QD material system for 1.3 µm is that of InAs on GaAs, i.e. InAs/GaAs QDs. Up till now, superior static performances had already been demonstrated for 1.3 µm InAs/GaAs QD lasers. To reduce the size and cost of the optical components, and improve the reliability of the overall system, it is preferred that the laser and electroabsorption modulator (EAM) are monolithically integrated. Among the various integration methods, the easiest one is to employ the identical active layer scheme where there is no need for epitaxial regrowth, selective epitaxy or post-growth treatment, e.g. intermixing. However, to exploit both the superior performances of 1.3 μm DFB QD lasers and the identical active layer scheme, there is a need to investigate the utilization of QDs for EAMs.