Quantum dot/ring tunable lasers on silicon through a novel ART buffer technology

Lead Research Organisation: Lancaster University
Department Name: Physics

Abstract

This project aims to develop advanced antimonide quantum dot/ring and its monolithic epitaxy on silicon to demonstrate widely tunable lasers for two different specific uses: one is the tunable lasers on silicon operating in O, C and H bands for telecom use and tunable mid-infrared lasers for gas analyser. The project fits into two priority areas in Industrial Strategy Challenge Fund: transformative digital technologies and quantum technologies.

Two industrial partners will be actively involved in this project including ZTE Photonics Co. Ltd (China) and Cascade Technologies (UK). There are cash inputs from the partners:

ZTE has invested £47k to the group to develop quantum materials and optoelectronic devices in collaboration with UESTC (2016-2018). In April 2017, with their support, we were also funded through a consortium of Silicon Photonics for Future Systems (£33K) to develop silicon-based quantum dot lasers.

Cascade Technologies and Lancaster has recently won a joint grant (the income to Lancaster: £150k) from Innovate UK to develop antimonide quantum dot lasers for gas analyser. This PhD will be nicely fit into this new grant.

Both companies are actively involved in the project, secondment opportunities would be provided to the PhD student; ZTE Photonics will host the student for two months (two visits) to investigate the modulation speed of the resulting quantum dot/ring tunable lasers using their state-of-the-art test instruments; Cascade Technologies will also offer secondment opportunities for 2 months to develop optical cavity dedicated to the QD lasers developed at Lancaster. The student will be trained for the use of companies' facilities and will be supervised by senior engineers from the company; the student will also learn about the management approaches of the companies, in particular with Cascade Technologies which is experienced in managing EU and Innovate UK research projects. The student should also develop the skills in lecturing - he/she will be the key contact to present the research outcomes to the companies and to intake the feedback from companies to achieve the next milestone.

This project requires expertise in MBE growth, materials characterization, device processing and nanofabrication. So it will be aligned with several academic staff including M. Hayne, Y. Pashkin, S. Kafanov and R. Young.

In addition, there is no PhD student could help to proceed these projects as both of my existing PhD students will graduate in April 2017. So this PhD studentship will be vital and timely to success these three research projects.

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/R512564/1 01/10/2017 30/09/2022
1959792 Studentship EP/R512564/1 01/10/2017 30/09/2021 Christopher Redman
 
Description 2 out of 3 main PhD objectives have been investigated and completed. We developed our existing gallium antimonide quantum rings on gallium arsenide structure by inserting the rings in an alloy sandwich of indium, gallium and arsenic, with a low concentration of indium to avoid heavy strain related effects. We stacked 3 repeated optically active layers on top of each other and then changed the position at which the rings are sat, from in the middle to at th ebottom. We characterised all of the samples with an in depth study by 1) taking micro-sized images of their surface to see how the rings look, and 2) taking their optical finger prints. It was concluded that we had significantly improved it's optical and thermal properties with an asymmetric structure. In particular we observed: brighter samples, purer emission (reduced linewidth) in the first telecom band (1.3 micrometers), and higher temperatures at which emission quenches which means a laser processed from these structures will lase better at room temperature. From this study we are exploring why the linewidth initially drops very sharply when increasing power at low power.

We attempted to increase the wavelength at which this sample emits at in order to reach deeper into the telecom bands, but unfortunately we found that adding indium does not increase the wavelength as expected (actually does the opposite and makes the wavelength shorter), nor does varying the thickness of the semiconductor sandwich shunt the wavelength far enough. This has opened up further on-going investigation into whether strain is ruining the structural quality of the rings during growth.

I have been trained extensively in molecular beam epitaxy to the point at which I am authorised to help with system maintenance under supervision and took part in system upgrades. I have learned how to conduct photoluminescence, atomic force microscopy, x-ray diffraction and hall effect measurements. Cleanroom training has started to complete the second half of my project which involves photolithography and strong acid work. This will be invaluable training both in academia and industry. A lot of effort also went into improving my presentation skills and analysis to a professional standard. I have also developed the way I approach and conduct my research, especially with how to efficiently read and review vast amounts of literature. I spent approximately 250 hours developing my teaching skills. I have learnt how to use fundamental software for physicists and engineers, i.e. Origin and Autocad, along with developing my coding ability in Python whilst refreshing some knowledge in Labview. I am also trained in COSHH and risk assessments and used my knowledge to assist with maintaining strict safety in the lab.
Exploitation Route Currently indium arsenide quantum dots dominate the research field. This material system is still relatively new and demonstrating improved characteristics may further pique the interest of others interested in quantum dot/ring lasers. This research has the potential to compete with the most commonly used commercial 1.3 micron quantum structure, should further developments be made, or other types of structure explored. This could easily be taken forward with my own research interests post graduation, or used by others to develop their own technologies.
Sectors Chemicals,Creative Economy,Digital/Communication/Information Technologies (including Software),Education,Electronics,Energy,Manufacturing, including Industrial Biotechology

 
Description Physics Staff Advisory Comittee Postgrad Rep
Geographic Reach Local/Municipal/Regional 
Policy Influence Type Participation in a advisory committee
Impact Listened to the rest of the postgrads and took any complaints and positive feedback to the committee. Small matters were raised to the department such as ensuring showers function properly and appropriate recycling access. Negative feedback regarding pay vs. workload was a common theme and the department is continuing to do its best to reach fair compromise on both sides. This helped build my team work and communication skills.
 
Description Risk Assessment for lone working
Geographic Reach Local/Municipal/Regional 
Policy Influence Type Influenced training of practitioners or researchers
 
Description Student Staff Consultative Committee Postgrad Rep
Geographic Reach Local/Municipal/Regional 
Policy Influence Type Participation in a advisory committee
Impact Similar to the other committee, however for this I set up a postgrad forum and lightning talk competition. This enhanced my planning and organisation skills.
 
Title MBE Growth 
Description Developed our quantum ring in quantum well structure. 
Type Of Material Improvements to research infrastructure 
Year Produced 2019 
Provided To Others? Yes  
Impact We found improved thermal properties from our developed structure. 
 
Title MBE Upgrades/Servicing 
Description Installed new components and upgraded/replaced parts on MBE system. 
Type Of Material Improvements to research infrastructure 
Year Produced 2019 
Provided To Others? Yes  
Impact Can now check gas leaks on the MBE system. Broken parts were fixed, system maintained in full working condition. Gained and in-depth understanding of how an MBE system works. Learnt how to fit specific parts and replace them, e.g. ion gauge filaments, RHEED screen, etc. 
 
Title Microstat clamp 
Description Developed the mechanical design for a clamp stand for the new PL system's cryostat and had it built. 
Type Of Material Improvements to research infrastructure 
Year Produced 2017 
Provided To Others? Yes  
Impact Allows the alignment of the laser between cryostat and spectrometer. Learnt how to use Autocad 
 
Title PL Measurements 
Description Had a lot of difficulty in measuring photoluminescence via fibre cable. Devised a measurement technique in order to optimise the temperature sweep and obtain more regulated step increments of temperature with each scan. 
Type Of Material Improvements to research infrastructure 
Year Produced 2018 
Provided To Others? Yes  
Impact This allowed me to measure my samples as accurately as reasonably possible. 
 
Title PL Shield 
Description Designed a shield and had it built to protect PL equipment user from dangerous laser light during measurement. 
Type Of Material Improvements to research infrastructure 
Year Produced 2018 
Provided To Others? Yes  
Impact Developed my knowledge of using Autocad. This shield protects the user's safety. 
 
Title Photolithography Mask 
Description Designed and had a mask manufactured for use in the cleanroom. UV light shines through the clear windows in this mask and onto the silicon wafer coated in a chemical that reacts with light and weakens for etching. 
Type Of Material Improvements to research infrastructure 
Year Produced 2019 
Provided To Others? Yes  
Impact I developed my knowledge using Autocad and learned how to use KLayout. I am now also able to undergo training and start the next part of my project. 
 
Title Critical Thickness Calculation 
Description Calculated critical thickness at which strain provokes the onset of the S-K growth mode as a function of indium composition for InGaAs. 
Type Of Material Computer model/algorithm 
Year Produced 2018 
Provided To Others? Yes  
Impact This gave us a rough idea of the quantum well thicknesses to use in our work. Solidified understanding of growth concepts. 
 
Title Growth Database 
Description Record of all growths performed to date and their corresponding PL and AFM (XRD where appropriate) characterisation. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? No  
Impact Maintained good organisation and made it easier to compare samples at a later date. Learning how to summarise data more efficiently has improved my presentation skills. Moreover this database allowed me to prepare for future growths. 
 
Title PL Analysis 
Description I revised our analytic method to better decompose spectra into subpeaks and appropriately account for background at high temperatures. Extensive amounts of background theory learned in order to complement my analysis. 
Type Of Material Data analysis technique 
Year Produced 2019 
Provided To Others? No  
Impact Accuracy of results is much improved and results seem more realistic now background is properly accounted for. More grounded with specialist knowledge in this area. 
 
Description UESTC 
Organisation University of Electronic Science and Technology of China (UESTC)
Country China 
Sector Academic/University 
PI Contribution I started working on my literature review and chaired the final session at the international Quantum Summit conference '17 in Chengdu. This further grew my collaboration network and my confidence in speaking.
Collaborator Contribution Offered valuable information through many helpful discussions.
Impact Made contacts with academics from the UESTC and other institutions from the conference.
Start Year 2017