Dr Robert Richards
PhD, MPhys
Department of Electronic and Electrical Engineering
Lecturer in Semiconductor Materials
Sheffield Bismide Semiconductors Research Group
Semiconductor Materials and Devices Research Group
+44 114 222 5148
Full contact details
Department of Electronic and Electrical Engineering
- Profile
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I studied physics at the University of Sheffield, gaining an MPhys in 2009. I then enrolled in the E-Futures Doctoral Training Centre, working on a variety of energy related projects from molecular biology through to mechanical engineering.
In late 2010 I started my PhD in Sheffield on photovoltaic characterisation, working with the Imperial College London spin-out company Quantasol.
Following the sale of Quantasol in 2011, I moved into molecular beam epitaxy (MBE) and gained my PhD in the MBE growth and characterisation of dilute bismide materials in 2014.
I was awarded an EPSRC Prize Fellowship to continue this work throughout 2015 and remained in the Semiconductor Materials and Devices group as a PDRA throughout 2016.
During this time I was awarded a Royal Academy of Engineering research fellowship, which started in 2017. Through this fellowship I am working on the development of MBE growth techniques for producing infrared optoelectronic devices.
The development of modern electronic devices has been driven by breakthroughs in functional materials. The realisation of gallium nitride devices gave us blue LEDs, blu-ray players, and white light LEDs; recent improvements in television technology have been triggered by the advent of organic LEDs and progress in quantum dot production.
My interest is in the development of highly mismatched alloys (HMAs) for next generation opto-electronic devices. These are devices that manipulate the interaction between photons and electrons, such as LEDs, lasers or solar cells.
HMAs are material systems wherein one of the component elements is significantly larger or smaller than the others. This mismatch makes the synthesis of these materials very challenging, but also endows them with unique opto-electronic properties.
- Qualifications
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- PhD in Electronic and Electrical Engineering, 2014, E-Futures Doctoral Training Centre, The University of Sheffield
- MPhys in Physics, 1st class, 2009, The University of Sheffield.
- Research interests
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- Dilute bismide semiconductor growth and characterisation
- Publications
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Journal articles
- Effects of rapid thermal annealing on deep-level defects and optical properties of n-type GaAsBi alloys grown by molecular beam epitaxy at low temperature. Materials Science in Semiconductor Processing, 169, 107888-107888.
- Negative thermal quenching in optically pumped GaAsBi–GaAs heterojunction p–i–n diode. Applied Physics A, 129(8).
- Opto-Electronic Characterisation of GaAsBi/GaAs Multiple Quantum Wells for Photovoltaic Applications. Solid State Phenomena, 343, 99-104.
- Exploring the formation of InAs(Bi)/GaAs QDs at two growth-temperature regimes under different Bi supply conditions. Applied Surface Science, 607, 154966-154966.
- Growth of GaAsBi/GaAs multiple quantum wells with up to 120 periods. Journal of Crystal Growth, 589.
- Growth of InAs(Bi)/GaAs quantum dots under a bismuth surfactant at high and low temperature. Journal of Nanomaterials, 2022.
- GaAsBi: From Molecular Beam Epitaxy Growth to Devices. physica status solidi (b), 259(2), 2270004-2270004.
- Effect of MBE growth conditions on GaAsBi photoluminescence lineshape and localised state filling.. Sci Rep, 12(1), 797.
- GaAsBi: from molecular beam epitaxy growth to devices. physica status solidi (b).
- Molecular beam epitaxial growth of GaAs/GaNAsBi core–multishell nanowires. Applied Physics Express, 14(11).
- Valence band engineering of GaAsBi for low noise avalanche photodiodes. Nature Communications, 12(1).
- Modelling of bismuth segregation in InAsBi/InAs superlattices: Determination of the exchange energies. Applied Surface Science, 485, 29-34. View this article in WRRO
- Light-biased IV characteristics of a GaAsBi/GaAs multiple quantum well pin diode at low temperature. Semiconductor Science and Technology, 33(9). View this article in WRRO
- Analysis of Bi Distribution in Epitaxial GaAsBi by aberration-corrected HAADF-STEM.. Nanoscale Research Letters, 13(1). View this article in WRRO
- Assessing the Nature of the Distribution of Localised States in Bulk GaAsBi.. Scientific Reports, 8(1). View this article in WRRO
- Photovoltaic characterisation of GaAsBi/GaAs multiple quantum well devices. Solar Energy Materials and Solar Cells, 172, 238-243. View this article in WRRO
- Deep-level defects in n-type GaAsBi alloys grown by molecular beam epitaxy at low temperature and their influence on optical properties. Scientific Reports, 7(1). View this article in WRRO
- Optical and spin properties of localized and free excitons in GaBi ₓAs₁-ₓ /GaAs multiple quantum wells. Journal of Physics D: Applied Physics, 49(35). View this article in WRRO
- Optical properties of GaAsBi/GaAs quantum wells: Photoreflectance, photoluminescence and time-resolved photoluminescence study. Semiconductor Science and Technology, 30(9), 094005-094005.
- Growth and structural characterization of GaAsBi/GaAs multiple quantum wells. Semiconductor Science and Technology, 30(9), 094013-094013.
- Bismuth concentration inhomogeneity in GaAsBi bulk and quantum well structures. Semiconductor Science and Technology, 30(9), 094018-094018.
- MBE grown GaAsBi/GaAs multiple quantum well structures: Structural and optical characterization. Journal of Crystal Growth, 425, 237-240. View this article in WRRO
- Absorption properties of GaAsBi based p–i–n heterojunction diodes. Semiconductor Science and Technology, 30(9), 094004-094004.
- Scanning transmission electron microscopy measurement of bismuth segregation in thin Ga(As,Bi) layers grown by molecular beam epitaxy. Crystal Research and Technology, 50(1), 38-42. View this article in WRRO
- Experimental and theoretical studies of band gap alignment in GaAs1−xBix/GaAs quantum wells. Journal of Applied Physics, 116(23), 233508-233508.
- Localization effects and band gap of GaAsBi alloys. physica status solidi (b), 251(6), 1276-1281.
- Demonstration of InAsBi photoresponse beyond 3.5 μm. Applied Physics Letters, 104(17), 171109-171109.
- Molecular beam epitaxy growth of GaAsBi using As2 and As4. Journal of Crystal Growth, 390, 120-124.
- Formation of Tetragonal InBi Clusters in InAsBi/InAs(100) Heterostructures Grown by Molecular Beam Epitaxy. Applied Physics Express, 6(11), 112601-112601.
- GaAsBi MQWs for multi-junction photovoltaics. 2013 IEEE 39th Photovoltaic Specialists Conference (PVSC).
- Effects of rapid thermal annealing on GaAs1-xBix alloys. Applied Physics Letters, 101(1), 012106-012106.
- Absorption Characteristics of ${rm GaAs}_{1-x}{rm Bi}_{x}/{rm GaAs}$ Diodes in the Near-Infrared. IEEE Photonics Technology Letters, 24(23), 2191-2194.
- Exploring the Implementation of GaAsBi Alloys as Strain-Reducing Layers in InAs/GaAs Quantum Dots. Nanomaterials, 14(4), 375-375.
- Temperature and band gap dependence of GaAsBi p-i-n diode current-voltage behaviour. Journal of Physics D: Applied Physics.
- Thermal Imaging Metrology Using High Dynamic Range Near-Infrared Photovoltaic-Mode Camera. Sensors, 21(18), 6151-6151.
Chapters
- Dilute Bismide Photodetectors, Bismuth-Containing Alloys and Nanostructures (pp. 299-318). Springer Singapore
Conference proceedings papers
- Effect of biasing under illumination on GaAsBi/GaAs multiple quantum wells for solar cell performance. 2023 IEEE Regional Symposium on Micro and Nanoelectronics (RSM), 28 August 2023 - 30 August 2023.
- Effect of bismuth flux on the optical and morphological properties of GaAsBi grown by Molecular Beam Epitaxy. 2022 IEEE 8th International Conference on Smart Instrumentation, Measurement and Applications (ICSIMA), 26 September 2022 - 28 September 2022.
- GaAsBi light emitting diodes for 1050nm broadband light sources. Biomedical Spectroscopy, Microscopy, and Imaging II, 3 April 2022 - 23 May 2022.
- CuZnS hole contacts on monocrystalline CdTe solar cells. 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC), 25 June 2017 - 30 June 2017.
- Influence of Growth Conditions on the Structural and Opto-electronic Quality of GaAsBi. Journal of Crystal Growth, Vol. 477(Proceeding of the 19th International Conference on Molecular Beam Epitaxy) (pp 139-143). Le Corum - Montepllier, France, 4 September 2016 - 9 September 2016. View this article in WRRO
- GaAsBi: An alternative to InGaAs based multiple quantum well photovoltaics. 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC), 5 June 2016 - 10 June 2016. View this article in WRRO
- Telecommunication wavelength GaAsBi light emitting diodes. IET Optoelectronics, Vol. 10(2) (pp 34-38) View this article in WRRO
- The effect of growth conditions to the optical quality of GaAsBi alloy. 2015 IEEE Regional Symposium on Micro and Nanoelectronics (RSM), 19 August 2015 - 21 August 2015.
- InAsBi photodiode operating in the MWIR. 2014 IEEE Photonics Conference, 12 October 2014 - 16 October 2014.
- Photoluminescence from localized states in GaAsBi epilayers. 2014 IEEE International Conference on Semiconductor Electronics (ICSE2014), 27 August 2014 - 29 August 2014.
- Demonstration of an InAsBi photodiode operating in the MWIR. Emerging Technologies in Security and Defence II; and Quantum-Physics-based Information Security III
- Effects of rapid thermal annealing on deep-level defects and optical properties of n-type GaAsBi alloys grown by molecular beam epitaxy at low temperature. Materials Science in Semiconductor Processing, 169, 107888-107888.
- Grants
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- 2015 - Development of InAsBi Quantum Dots as Single Photon Emitters for Quantum Technology
- Royal Academy of Engineering research fellowship: Development of indium gallium arsenide bismide for mid-wavelength infrared applications
- Professional activities and memberships
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- Royal Academy of Engineering Post-doctoral Research Fellow
- UK Semiconductors Conference organising committee member
- Postdoctoral Fellowship College mentor