Deng, Huiwen;
(2024)
Doping Strategies of InAs/GaAs Quantum Dot Lasers.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
III-V InAs quantum dot (QD) Lasers are renowned for their high-temperature (HT) stability, low threshold current, and defect insensitivity. These lasers provide flexible wavelength options for various applications. However, there are challenges in controlling the formation and self-organisation of QDs. These issues lead to limitations in areal density and size distribution, causing inhomogeneous broadening and a broader emission spectrum, which diminishes modal gain. To tackle these challenges, this thesis focuses on optimising the growth and doping of InAs/GaAs QDs. Through extensive experimentation and fine-tuning of growth conditions, a significant improvement in the QD density and optical properties was achieved. This improvement is evidenced by improved photoluminescence (PL), a narrower emission spectrum with a full width at half maximum (FWHM) of 30.11 meV, and a QD density of 6.5 × 10¹⁰ cm⁻². Significant progress has also been made in the field of doping techniques. The introduction of direct n-type doping during QD formation allows for precise control of the dopant density. This advancement has led to increased PL intensity, higher slope efficiency, elevated laser operation temperatures, and a reduced threshold current density. Additionally, the use of p-type modulation doping has effectively countered the thermal excitation effects on holes in QD lasers, thus improving their temperature stability (T0 ). Moreover, a novel doping technique, named the co-doping method, combines both n-type and p-type doping. This technique has produced lasers with exceptionally low threshold current densities and high slope efficiencies. These codoped lasers maintain robust performance even at high temperatures, including up to 195 °C. In continuous wave mode, these co-doped lasers demonstrate outstanding attributes, including notably low threshold current densities and high slope efficiencies at room temperature.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Doping Strategies of InAs/GaAs Quantum Dot Lasers |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2024. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10192637 |
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