Professor David Mowbray
Professor of Physics
- Room: E19
- Phone: +44 (0)114 222 4561
- Email: firstname.lastname@example.org
- Personal webpage http://www.sheffield.ac.uk/physics/contacts/david-mowbray
My research involves the application of a range of optical spectroscopic techniques to study physical processes in III-V semiconductors and related nanostructures and devices. Particular interests are wide band gap materials (AlGaInP and (Al)InGaN) for visible and uv light emitters and quantum dots for high efficiency lasers and novel light emitters. I was the first person to deduce the band structure of AlGaInP, a semiconductor now used as the basis for high efficiency red, orange and yellow LEDs and red lasers. I have developed 1.3 um emitting lasers using InAs self-assembled quantum dots which exhibit extremely low operating currents and high temperature stability. A recent project developed quantum dots lasers on Si substrates, providing the potential for the direct integration of III-V light emitters with Si CMOS electronics. My current research is a joint project with colleagues at UCL and Warwick to grow and study quantum dots placed within quantum wires. This offers the prospect for high efficiency single photon sources and nanoscale lasers.
Physics BA (1981-1984, Hertford College, Oxford University)
PDRA Department of Physics, Oxford University 1987-1989
Head of Teaching 2004-2012
Member of Senate 2006-2012
Member of the Institute of Physics
My recent research has focussed on the application of self-assembled quantum dots to produce high efficiency semiconductor lasers. Conventional semiconductor lasers have many desirable properties but their operating current (threshold current) can be high and this current typically increases rapidly with increasing temperature. By using quantum dots as the light emitting region it is possible to reduce significantly both the operating current and the temperature sensitivity of this current.
By optimising the epitaxial growth myself and co-workers were able to produce InAs self-assembled quantum dots lasers emitting at 1.3 um with threshold current densities much smaller than comparable quantum well lasers and at the time the lowest ever reported. Later work applied p-type modulation doping to obtain high stability at room temperature.
My current work focuses on the study of a new type of quantum dot. These are grown within long nanowires that form from small holes made in an inert layer on a semiconductor substrate or metallic particles deposited on a semiconductor surface. Unlike self-assembled quantum dots, which form at random position, these nanowire quantum dots can be made to form at pre-definied positions. In addition there is considerably more control over their shape and size and it is possible to form stacks with a large number of identical dots, allowing the formation of nanoscale lasers. The nanowire may act as an optical cavity to give very high light extraction for optical emitters. This project is a collaboration with University College London and the University of Warwick.
Recent research funding
EPSRC InAs quantum dot lasers on Si substrates April 2012 – March 2016
Year 2 Physics Tutor
Year 4 project supervision
Recent undergraduate projects supervised
The physics of digital photography (year 3)
Optical spectroscopy of semiconductor nanowires incorporating quantum dots (year 4)
Key Scientific Publications
Observation of a many-body edge singularity in quantum well luminescence spectra. M S Skolnick, J M Rorison, K J Nash D J Mowbray, P R Tapster, S J Bass and A D Pitt. Phys. Rev. Lett. 58 2130-2133 (1987).
Confined LO phonons in GaAs/AlAs superlattices. D J Mowbray, M Cardona and K Ploog. Phys. Rev. B. 43 1598-1603 (1991).
Valence-band splitting in ordered Ga0.5In0.5P measured by polarized photoluminescence excitation spectroscopy. D J Mowbray, R A Hogg, M S Skolnick, M C DeLong, S R Kurtz and J M Olson. Phys. Rev. B. 46 7232-7235 (1992).
Electronic Band Structure of AlGaInP Grown by Solid-Source Molecular Beam Epitaxy. D J Mowbray, O P Kowalski, M Hopkinson, M S Skolnick and J P R David. Appl. Phys. Lett. 65, p213-215 (1994).
GaInP-AlGaInP Band Offsets Determined from Hydrostatic Pressure Measurements. O P Kowalski, J W Cockburn, D J Mowbray, M S Skolnick, R Teissier and M Hopkinson. Appl. Phys. Lett. 66, p619-621 (1995)
Inverted electron-hole alignment in InAs-GaAs self-assembled quantum dots P W Fry, I E Itskevich, D J Mowbray, M S Skolnick, J Barker, E P O'Reilly, L R Wilson, I A Larkin, P A Maksym, M Hopkinson, M Al-Khafaji, J P R David, A G Cullis, G Hill and J C Clark Phys. Rev. Lett. 84, 733 (2000)
Charged and neutral exciton complexes in individual self-assembled In(Ga)As quantum dots J J Finley, A D Ashmore, A Lemaitre, D J Mowbray, M S Skolnick, I E Itskevich, P A Maksym, M Hopkinson and T F Krauss Phys. Rev. B 63, 073307 (2001)
1.3 m InAs/GaAs multilayer quantum-dot laser with extremely low room-temperature threshold current density I R Sellers, H Y Liu, K M Groom, D T Childs, D Robbins, T J Badcock, M Hopkinson, D J Mowbray and M S Skolnick Electron. Lett. 40, 1412 (2004)
1.3 m InAs/GaAs quantum-dot laser with low-threshold current density and negative characteristic temperature above room temperature T J Badcock, H Y Liu, K M Groom, C Y Jin, M Gutierrez, M Hopkinson, D J Mowbray and M S Skolnick Electron. Letts. 42, 922 (2006)
Room-temperature 1.6 m light emission from InAs/GaAs quantum dots with a thin GaAsSb cap layer H Y Liu, M J Steer, T J Badcock, D J Mowbray, M S Skolnick, F Suarez, J S Ng, M Hopkinson and J P R David J. Appl. Phys. 99, 046104 (2006)
Infrared modulated interlevel spectroscopy of 1.3 mu m self-assembled quantum dot lasers using a free electron laser I R Sellers, D J Mowbray, T J Badcock, J P R Wells, P J Phillips, D A Carder, H Y Liu, K M Groom and M Hopkinson Appl. Phys. Lett. 88, 081108 (2006)
Picosecond carrier dynamics in AllnGaN multiple quantum wells S A Hashemizadeh, J P R Wells, P Murzyn, J Brown, B D Jones, T Wang, P J Parbrook, A M Fox, D J Mowbray and M S Skolnick Appl. Phys. Lett. 87, 232106 (2005)
Enhanced room-temperature quantum-dot effects in modulation-doped InAs/GaAs quantum dots Y D Jang, J Park, D Lee, D J Mowbray, M Skolnick, H YLiu, M Hopkinson, R A Hogg, Appl. Phys. Lett. 95 171902 (2009)
Competitive carrier interactions influencing the emission dynamics of GaAsSb-capped InAs quantum dots Pavarelli, N. Ochalski, T. J. Liu, H. Y. Gradkowski, K. Schmidt, M.Williams, D. P. Mowbray, D. J. Huyet, G. Appl Phys Lett 101 DI 10.1063/1.4769431(2012)
In situ annealing enhancement of the optical properties and laser device performance of InAs quantum dots grown on Si substrates Jonathan R. Orchard1, Samuel Shutts, Angela Sobiesierski, Jiang Wu, Mingchu Tang, Siming Chen, Qi Jiang, Stella Elliott, Richard Beanland, Huiyun Liu, Peter M. Smowton, David J. Mowbray Optics Express March (2016)
Silicon-Based Single Quantum Dot Emission in the Telecoms C-Band
Jonathan R. Orchard, Chris Woodhead, Jiang Wu, Mingchu Tang, Richard Beanland, Yasir Noori, Huiyun Liu, Robert J. Young and David J. Mowbray
Chapter on Inorganic Semiconductor Nanostructures in ‘Nanoscale Science and Technology’ edited by R Kelsall, I W Hamley and M Geoghegan Wiley 2005 ISBN: 978-0-470-85086-2
Quantum dots spot single photons
Self-assembled semiconductor quantum dots: Fundamental physics and device applications
Recent developments in the physics and applications of self-assembled quantum dots
Quantum-dot lasers close in on their quantum-well rivals
New physics and devices based on self-assembled semiconductor quantum dots
Schools Outreach Talks
Electricity (primary school)