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Professor David Wallis
(he/him)
- Available for postgraduate supervision
Teams and roles for David Wallis
Professor - Compound Semiconductors
Academic Interface Director, Institute for Compound Semiconductors
Overview
Gallium Nitride is a new semiconductor that is delivering a revolution in the performance and efficiency of LEDs and transistors. My research focuses on the development of epitaxial growth and device technologies in this material. In particular, I am developing GaN on Si that will deliver the next generation of low cost GaN electronic devices and cubic-GaN, which will significantly improve the efficiency and quality of LED lighting. I have also recently launched a spin-out company, Kubos semiconductors, which will commercially develop the cubic GaN growth technology based on my research.
Publication
2025
- Adams, F. et al., 2025. Behaviour of Ti/Al/Ti/Au contacts to AlGaN/GaN heterostructures at low temperature. Journal of Physics D: Applied Physics 58 (13) 135117. (10.1088/1361-6463/adafb5)
- Dyer, D. et al., 2025. Broadly tunable cubic phase InGaN/GaN quantum wells grown by metal-organic chemical vapor deposition.. Presented at: OPTO: Gallium Nitride Materials and Devices XX San Francisco, CA, USA 25-31 January 2025. Published in: Fujioka, H. , Morkoc, H. and Schwarz, U. T. eds. Proceedings Volume 13366, Gallium Nitride Materials and Devices XX. SPIE. (10.1117/12.3039278)
- Ghosh, S. et al., 2025. Buffer-less gallium nitride high electron mobility heterostructures on silicon. Advanced Materials 37 (9) 2413127. (10.1002/adma.202413127)
- Shu, R. et al., 2025. Beyond transmission electron microscopy imaging: atom probe tomography reveals chemical inhomogeneity at stacking fault interfaces in InGaN/GaN light-emitting diodes. Materialia 40 102417. (10.1016/j.mtla.2025.102417)
- Xu, X. et al., 2025. Effect of buffer layer thickness on recombination in zincblende InGaN/GaN quantum wells. Journal of Physics D: Applied Physics 58 (47) 475101. (10.1088/1361-6463/ae1d8d)
- Xu, X. et al., 2025. Point defect luminescence associated with stacking faults in magnesium doped zincblende GaN. Journal of Applied Physics 137 (23) 235301. (10.1063/5.0274599)
2024
- Chen, C. et al., 2024. Threshold voltage mapping at the nanoscale of GaN-based high electron mobility transistor structures using hyperspectral scanning capacitance microscopy. Applied Physics Letters 124 (23) 232107. (10.1063/5.0203646)
- Dyer, D. et al., 2024. Efficiency droop in zincblende InGaN/GaN quantum wells. Nanoscale 16 (29), pp.13953-13961. (10.1039/D4NR00812J)
- Gundimeda, A. et al., 2024. Cathodoluminescence studies of the optical properties of a zincblende InGaN/GaN single quantum well. Nanotechnology 35 (39) 395705. (10.1088/1361-6528/ad5db4)
- Gundimeda, A. et al., 2024. Impact of stacking faults on the luminescence of a zincblende InGaN/GaN single quantum well. Journal of Physics D: Applied Physics 58 (2) 025112. (10.1088/1361-6463/ad8662)
- Shi, C. et al., 2024. A circuit for evaluating GaN HEMT dynamic Rds(on) at cryogenic temperatures. Presented at: 9th Southern Power Electronics Conference (SPEC) Brisbane, Australia 2-5 December 2024. Proceedings of 9th Southern Power Electronics Conference. IEEE. , pp.1-6. (10.1109/spec62217.2024.10893110)
2023
- Chen, C. et al., 2023. Scanning capacitance microscopy of GaN-based high electron mobility transistor structures: A practical guide. Ultramicroscopy 254 113833. (10.1016/j.ultramic.2023.113833)
- Ghosh, S. et al., 2023. Design of step-graded AlGaN buffers for GaN-on-Si heterostructures grown by MOCVD. Semiconductor Science and Technology 38 (4) 044001. (10.1088/1361-6641/acb9b6)
- Hinz, A. M. et al., 2023. Strategy for reliable growth of thin GaN Caps on AlGaN HEMT structures. Journal of Crystal Growth 624 127420. (10.1016/j.jcrysgro.2023.127420)
- Leigh, W. et al. 2023. Monitoring of the initial stages of diamond growth on aluminum nitride using in situ spectroscopic ellipsometry. ACS Omega 8 (33), pp.30442-30449. (10.1021/acsomega.3c03609)
- Wade, T. et al., 2023. MOVPE studies of zincblende GaN on 3C-SiC/Si(0 0 1). Journal of Crystal Growth 611 127182. (10.1016/j.jcrysgro.2023.127182)
- Wadsworth, A. et al., 2023. GaN-based cryogenic temperature power electronics for superconducting motors in cryo-electric aircraft. Superconductor Science and Technology 36 (9) 094002. (10.1088/1361-6668/ace5e7)
- Xiu, H. et al., 2023. Polarity determination of crystal defects in zincblende GaN by aberration-corrected electron microscopy. Journal of Applied Physics 133 105302. (10.1063/5.0138478)
- Yang, H. et al., 2023. A cross-linkable, organic down-converting material for white light emission from hybrid LEDs. Journal of Materials Chemistry C Materials for optical and electronic devices 11 (29), pp.9984-9995. (10.1039/D2TC05139G)
2022
- Binks, D. J. et al., 2022. Cubic GaN and InGaN/GaN quantum wells. Applied Physics Reviews 9 041309. (10.1063/5.0097558)
- Gundimeda, A. et al., 2022. Investigation of wurtzite formation in MOVPE-grown zincblende GaN epilayers on AlxGa1−xN nucleation layers. Journal of Applied Physics 131 (11) 115703. (10.1063/5.0077186)
- Gundimeda, A. et al., 2022. Influence of AlxGa1-xN nucleation layers on MOVPE-grown zincblende GaN epilayers on 3C-SiC/Si(001). Journal of Physics D: Applied Physics 55 (7) 175110. (10.1088/1361-6463/ac4c58)
- Yin, Y. et al., 2022. Fabrication of semi-polar (11-22) GaN V-groove MOSFET using wet etching trench opening technique. IEEE Electron Device Letters 43 (10), pp.1641-1644. (10.1109/LED.2022.3203633)
2021
- Church, S. A. et al., 2021. Photoluminescence efficiency of zincblende InGaN/GaN quantum wells. Journal of Applied Physics 129 175702. (10.1063/5.0046649)
- Cuenca, J. A. et al. 2021. Thermal stress modelling of diamond on GaN/III-Nitride membranes. Carbon 174 , pp.647-661. (10.1016/j.carbon.2020.11.067)
- Dyer, D. et al., 2021. The effect of thermal annealing on the optical properties of Mg-doped zincblende GaN epilayers. Journal of Applied Physics 130 (8) 085705. (10.1063/5.0057824)
- Spiridon, B. F. et al., 2021. Method for inferring the mechanical strain of GaN-on-Si epitaxial layers using optical profilometry and finite element analysis. Optical Materials Express 11 (6), pp.1643-1655. (10.1364/OME.418728)
- Vacek, P. et al., 2021. Defect structures in (001) zincblende GaN/3C-SiC nucleation layers. Journal of Applied Physics 129 (15) 155306. (10.1063/5.0036366)
2020
- Church, S. A. et al., 2020. Stacking fault-associated polarised surface-emitted photoluminescence from zincblende InGaN/GaN quantum wells. Applied Physics Letters 117 (3) 032103. (10.1063/5.0012131)
- Ding, B. et al., 2020. Alloy segregation at stacking faults in zincblende GaN heterostructures. Journal of Applied Physics 128 (14) 145703. (10.1063/5.0015157)
- Sun, C. et al., 2020. Thin film gallium nitride (GaN) based acoustofluidic tweezer: modelling and microparticle manipulation. Ultrasonics 108 106202. (10.1016/j.ultras.2020.106202)
- Sun, C. et al., 2020. Gallium nitride: a versatile compound semiconductor as novel piezoelectric film for acoustic tweezer in manipulation of cancer cells. IEEE Transactions on Electron Devices 67 (8), pp.3355-3361. (10.1109/TED.2020.3002498)
- Wiles, A. A. et al., 2020. A poly(urethane)-encapsulated benzo[2,3-d:6,7-d’]diimidazole organic down-converter for green hybrid LEDs. Materials Chemistry Frontiers 4 (3), pp.1006-1012. (10.1039/C9QM00771G)
2019
- Angioni, E. et al., 2019. Implementing fluorescent MOFs as down-converting layers in hybrid light-emitting diodes. Journal of Materials Chemistry. C 7 (8), pp.2394-2400. (10.1039/C9TC00067D)
- Lee, L. Y. et al., 2019. Investigation of MOVPE-grown zincblende GaN nucleation layers on 3C-SiC/Si substrates. Journal of Crystal Growth 524 125167. (10.1016/j.jcrysgro.2019.125167)
- Lee, L. Y. et al., 2019. Investigation of stacking faults in MOVPE-grown zincblende GaN by XRD and TEM. Journal of Applied Physics 125 105303. (10.1063/1.5082846)
- Mandal, S. et al. 2019. Thick, adherent diamond films on AlN with low thermal barrier resistance. ACS Applied Materials and Interfaces 11 (43), pp.40826-40834. (10.1021/acsami.9b13869)
2018
- Choi, F. S. et al., 2018. Vertical leakage mechanism in GaN on Si high electron mobility transistor buffer layers. Journal of Applied Physics 124 (5) 055702. (10.1063/1.5027680)
- Church, S. A. et al., 2018. Effect of stacking faults on the photoluminescence spectrum of zincblende GaN. Journal of Applied Physics 123 (18) 185705. (10.1063/1.5026267)
- Roff, C. et al., 2018. Utilization of waveform measurements for degradation analysis of AlGaN/GaN HFETs. Presented at: ARFTG 70th Microwave Measurement Symposium Tempe, AZ, USA 27-30 November 2007. 2007 70th ARFTG Microwave Measurement Conference (ARFTG). IEEE. (10.1109/ARFTG.2007.8376173)
- Tang, F. et al., 2018. Nanoscale structural and chemical analysis of F-implanted enhancement-mode InAlN/GaN heterostructure field effect transistors. Journal of Applied Physics 123 (2) 024902. (10.1063/1.5006255)
- Yi, L. et al., 2018. Effect of growth temperature and V/III-ratio on the surface morphology of MOVPE-grown cubic zincblende GaN. Journal of Applied Physics 124 105302.
- Zaidi, Z. H. et al., 2018. Effects of surface plasma treatment on threshold voltage hysteresis and instability in metal-insulator-semiconductor (MIS) AlGaN/GaN heterostructure HEMTs. Journal of Applied Physics 123 (18) 184503. (10.1063/1.5027822)
2017
- Benakaprasad, B. et al. 2017. Design and performance comparison of various terahertz microstrip antennas on GaN-on-low resistivity silicon substrates for TMIC. Presented at: Microwave Conference (APMC), Asia-Pacific New Delhi, India 5-9 Dec 2016. Proceedings of the Asia-Pacific Microwave Conference 2016. IEEE(10.1109/APMC.2016.7931368)
- Eblabla, A. et al. 2017. Passive components technology for THz-Monolithic Integrated Circuits (THz-MIC). Presented at: 18th International Radar Symposium (IRS), 2017 Prague, Czech Republic 28-30 June 2017. Radar Symposium Conference Proceedings. , pp.1-7. (10.23919/IRS.2017.8008166)
- Eblabla, A. M. et al. 2017. GaN on low-resistivity silicon THz high-Q passive device technology. IEEE Transactions on Terahertz Science & Technology 7 (1), pp.93-97. (10.1109/TTHZ.2016.2618751)
- Jiang, S. et al., 2017. All-GaN-integrated cascode heterojunction field effect transistors. IEEE Transactions on Power Electronics 32 (11), pp.8743-8750. (10.1109/TPEL.2016.2643499)
- Mandal, S. et al. 2017. Surface zeta potential and diamond seeding on gallium nitride films. ACS Omega 2 (10), pp.7275-7280. (10.1021/acsomega.7b01069)
- Rae, K. et al., 2017. InGaN µLEDs integrated onto colloidal quantum dot functionalized ultra-thin glass. Optics Express 25 (16), pp.19179-19184. (10.1364/OE.25.019179)
2016
- Benakaprasad, B. et al. 2016. Terahertz microstrip single patch antenna technology on GaN-on-Low resistivity silicon substrates for TMIC. Presented at: IET Colloquium on Antennas, Wireless and Electromagnetics Glasgow, UK 26 May 2016.
- Benakaprasad, B. et al. 2016. Terahertz monolithic integrated circuits (TMICs) array antenna technology on GaN-on-Low resistivity silicon substrates. Presented at: 41st International Conference on Infrared, Millimeter, and Terahertz waves (IRMMW-THz), Copenhagen, Denmark 25-30 Sep 2016. 2016 41st International Conference on Infrared, Millimeter, and Terahertz waves (IRMMW-THz),. IEEE(10.1109/IRMMW-THz.2016.7758488)
- Chatterjee, I. et al., 2016. Impact of buffer charge on the reliability of carbon doped AlGaN/GaN-on-Si HEMTs. Presented at: 2016 IEEE International Reliability Physics Symposium (IRPS) Pasadena, CA, USA 17-21 April 2016. 2016 IEEE International Reliability Physics Symposium (IRPS). IEEE. , pp.4A41-4A45. (10.1109/IRPS.2016.7574529)
- Eblabla, A. et al. 2016. High frequency active and passives devices using GaN on low resistivity silicon. Presented at: ARMMS RF & Microwave Society Conference Milton Common Nr Thame, UK 18-19 Apr 2016.
- Elgaid, K. et al. 2016. MMIC-compatible microstrip technology for GaN-HEMTs on low resistivity silicon substrate. Presented at: International Workshop on Nitride Semiconductors (IWN 2016) Orlando, FL, USA 2-7 Oct 2016.
- Jamil, S. et al., 2016. Standby person for electrical tasks and rescue guidelines for electrical incident victims. Presented at: Petroleum and Chemical Industry Technical Conference (PCIC) Philadelphia, PA, USA 19-22 Sep 2016. IEEE(10.1109/PCICON.2016.7589220)
- Miaja, P. F. et al., 2016. Modelling the closely-coupled cascode switching process. Presented at: 2016 IEEE Energy Conversion Congress and Exposition (ECCE) Milwaukee, WI 18-22 September 2016. 2016 IEEE Energy Conversion Congress and Exposition (ECCE). IEEE(10.1109/ECCE.2016.7855268)
- Waller, W. M. et al., 2016. Subthreshold Mobility in AlGaN/GaN HEMTs. IEEE Transactions on Electron Devices 63 (5), pp.1861-1865. (10.1109/TED.2016.2542588)
- Wallis, D. 2016. The hazards of risk assessment. Presented at: Electrical Safety Workshop (ESW) Jacksonville, FL, USA 6-11 March 2016. (10.1109/ESW.2016.7499706)
2015
- Eblabla, A. et al. 2015. High performance GaN high electron mobility transistors on low resistivity silicon for X -Band Applications. IEEE Electron Device Letters 36 (9), pp.899-901. (10.1109/LED.2015.2460120)
- Eblabla, A. et al. 2015. Novel shielded coplanar waveguides on GaN-on-Low resistivity Si substrates for MMIC applications. IEEE Microwave and Wireless Components Letters 25 (7), pp.427-429. (10.1109/LMWC.2015.2429120)
- Waller, W. M. et al., 2015. Interface state artefact in long gate-length AlGaN/GaN HEMTs. IEEE Transactions of Electron Devices 62 (8), pp.2464-2469. (10.1109/TED.2015.2444911)
2010
- Ashley, T. et al., 2010. High-performance InSb based quantum well field effect transistors for low-power dissipation applications. Presented at: 2009 IEEE International Electron Devices Meeting (IEDM) Baltimore, MD, USA 7-9 December 2009. 2009 IEEE International Electron Devices Meeting (IEDM). IEEE. , pp.1. (10.1109/IEDM.2009.5424207)
2009
- Janssen, J. et al., 2009. X-Band GaN SPDT MMIC with over 25 watt linear power handling. Presented at: European Microwave Integrated Circuit Conference, 2008 Amsterdam, The Netherlands 27-28 October 2009. 2008 European Microwave Integrated Circuit Conference. IEEE(10.1109/EMICC.2008.4772261)
- Riedel, G. J. et al., 2009. Reducing thermal resistance of AlGaN/GaN electronic devices using novel nucleation layers. IEEE Electron Device Letters 30 (2), pp.103-106. (10.1109/LED.2008.2010340)
2008
- Radosavljevic, M. et al., 2008. High-performance 40nm gate length InSb p-channel compressively strained quantum well field effect transistors for low-power (VCC=0.5V) logic applications. Presented at: IEEE International Electron Devices Meeting San Francisco, CA 15-17 Dec 2008. (10.1109/IEDM.2008.4796798)
- Riedel, G. et al., 2008. Nanosecond timescale thermal dynamics of AlGaN/GaN electronic devices. IEEE Electron Device Letters 29 (5), pp.416-418. (10.1109/LED.2008.919779)
2007
- Ashley, T. et al., 2007. Heterogeneous InSb quantum well transistors on silicon for ultra-high speed, low power logic applications. Electronics letters 43 (14) 777. (10.1049/el:20071335)
- Ashley, T. et al., 2007. Indium antimonide based quantum well FETs for ultra-high speed electronics. Presented at: 64th Device Research Conference State College, PA 26-28 June 2006. , pp.201. (10.1109/DRC.2006.305056)
- Kuball, M. et al., 2007. Time-resolved temperature measurement of AlGaN/GaN electronic devices using micro-raman spectroscopy. IEEE Electron Device Letters 28 (2), pp.86-89. (10.1109/LED.2006.889215)
- Sarua, A. et al., 2007. Thermal boundary resistance between GaN and substrate in AlGaN/GaN electronic devices. IEEE Transactions of Electron Devices 54 (12), pp.3152-3158. (10.1109/TED.2007.908874)
2006
- Ashley, T. et al., 2006. Indium antimonide based technology for RF applications. Presented at: Compound Semiconductor Integrated Circuit Symposium San Antonio, TX 12-15 Nov 2006. (10.1109/CSICS.2006.319918)
- Uren, M. et al., 2006. Control of Short-Channel Effects in GaN/AlGaN HFETs. Presented at: 1st European Microwave Integrated Circuits Conference Manchester, UK 10-13 Sept 2006. 2006 European Microwave Integrated Circuits Conference. IEEE. , pp.65-65. (10.1109/EMICC.2006.282751)
- Wallis, D. 2006. Class F at class B temperatures is it time for a change?. Presented at: Conference Record of the 2006 IEEE International Symposium on Electrical Insulation, 2006 Toronto, Ont., Canada 11-14 June 2006. (10.1109/ELINSL.2006.1665243)
2005
- Datta, S. et al., 2005. 85nm gate length enhancement and depletion mode InSb quantum well transistors for ultra high speed and very low power digital logic applications. Presented at: IEEE International Electron Devices Meeting Washington DC 5 Dec 2005. Electron Devices Meeting, 2005. IEDM Technical Digest. IEEE International. IEEE. (10.1109/IEDM.2005.1609466)
2001
- Wallis, D. et al. 2001. Measurement of III-V quaternary composition using X-ray diffraction. IEE Proceedings Optoelectronics 148 (2), pp.97-100. (10.1049/ip-opt:20010442)
1996
- Wallis, D. , Watson, A. and Mo, N. 1996. Cardiac neurones of automatic ganglia. Microscopy Research and Technique 35 (1), pp.69-79. (10.1002/(SICI)1097-0029(19960901)35:1<69::AID-JEMT6>3.0.CO;2-N)
Articles
- Adams, F. et al., 2025. Behaviour of Ti/Al/Ti/Au contacts to AlGaN/GaN heterostructures at low temperature. Journal of Physics D: Applied Physics 58 (13) 135117. (10.1088/1361-6463/adafb5)
- Angioni, E. et al., 2019. Implementing fluorescent MOFs as down-converting layers in hybrid light-emitting diodes. Journal of Materials Chemistry. C 7 (8), pp.2394-2400. (10.1039/C9TC00067D)
- Ashley, T. et al., 2007. Heterogeneous InSb quantum well transistors on silicon for ultra-high speed, low power logic applications. Electronics letters 43 (14) 777. (10.1049/el:20071335)
- Binks, D. J. et al., 2022. Cubic GaN and InGaN/GaN quantum wells. Applied Physics Reviews 9 041309. (10.1063/5.0097558)
- Chen, C. et al., 2023. Scanning capacitance microscopy of GaN-based high electron mobility transistor structures: A practical guide. Ultramicroscopy 254 113833. (10.1016/j.ultramic.2023.113833)
- Chen, C. et al., 2024. Threshold voltage mapping at the nanoscale of GaN-based high electron mobility transistor structures using hyperspectral scanning capacitance microscopy. Applied Physics Letters 124 (23) 232107. (10.1063/5.0203646)
- Choi, F. S. et al., 2018. Vertical leakage mechanism in GaN on Si high electron mobility transistor buffer layers. Journal of Applied Physics 124 (5) 055702. (10.1063/1.5027680)
- Church, S. A. et al., 2020. Stacking fault-associated polarised surface-emitted photoluminescence from zincblende InGaN/GaN quantum wells. Applied Physics Letters 117 (3) 032103. (10.1063/5.0012131)
- Church, S. A. et al., 2018. Effect of stacking faults on the photoluminescence spectrum of zincblende GaN. Journal of Applied Physics 123 (18) 185705. (10.1063/1.5026267)
- Church, S. A. et al., 2021. Photoluminescence efficiency of zincblende InGaN/GaN quantum wells. Journal of Applied Physics 129 175702. (10.1063/5.0046649)
- Cuenca, J. A. et al. 2021. Thermal stress modelling of diamond on GaN/III-Nitride membranes. Carbon 174 , pp.647-661. (10.1016/j.carbon.2020.11.067)
- Ding, B. et al., 2020. Alloy segregation at stacking faults in zincblende GaN heterostructures. Journal of Applied Physics 128 (14) 145703. (10.1063/5.0015157)
- Dyer, D. et al., 2024. Efficiency droop in zincblende InGaN/GaN quantum wells. Nanoscale 16 (29), pp.13953-13961. (10.1039/D4NR00812J)
- Dyer, D. et al., 2021. The effect of thermal annealing on the optical properties of Mg-doped zincblende GaN epilayers. Journal of Applied Physics 130 (8) 085705. (10.1063/5.0057824)
- Eblabla, A. et al. 2015. High performance GaN high electron mobility transistors on low resistivity silicon for X -Band Applications. IEEE Electron Device Letters 36 (9), pp.899-901. (10.1109/LED.2015.2460120)
- Eblabla, A. et al. 2015. Novel shielded coplanar waveguides on GaN-on-Low resistivity Si substrates for MMIC applications. IEEE Microwave and Wireless Components Letters 25 (7), pp.427-429. (10.1109/LMWC.2015.2429120)
- Eblabla, A. M. et al. 2017. GaN on low-resistivity silicon THz high-Q passive device technology. IEEE Transactions on Terahertz Science & Technology 7 (1), pp.93-97. (10.1109/TTHZ.2016.2618751)
- Ghosh, S. et al., 2025. Buffer-less gallium nitride high electron mobility heterostructures on silicon. Advanced Materials 37 (9) 2413127. (10.1002/adma.202413127)
- Ghosh, S. et al., 2023. Design of step-graded AlGaN buffers for GaN-on-Si heterostructures grown by MOCVD. Semiconductor Science and Technology 38 (4) 044001. (10.1088/1361-6641/acb9b6)
- Gundimeda, A. et al., 2022. Investigation of wurtzite formation in MOVPE-grown zincblende GaN epilayers on AlxGa1−xN nucleation layers. Journal of Applied Physics 131 (11) 115703. (10.1063/5.0077186)
- Gundimeda, A. et al., 2024. Cathodoluminescence studies of the optical properties of a zincblende InGaN/GaN single quantum well. Nanotechnology 35 (39) 395705. (10.1088/1361-6528/ad5db4)
- Gundimeda, A. et al., 2024. Impact of stacking faults on the luminescence of a zincblende InGaN/GaN single quantum well. Journal of Physics D: Applied Physics 58 (2) 025112. (10.1088/1361-6463/ad8662)
- Gundimeda, A. et al., 2022. Influence of AlxGa1-xN nucleation layers on MOVPE-grown zincblende GaN epilayers on 3C-SiC/Si(001). Journal of Physics D: Applied Physics 55 (7) 175110. (10.1088/1361-6463/ac4c58)
- Hinz, A. M. et al., 2023. Strategy for reliable growth of thin GaN Caps on AlGaN HEMT structures. Journal of Crystal Growth 624 127420. (10.1016/j.jcrysgro.2023.127420)
- Jiang, S. et al., 2017. All-GaN-integrated cascode heterojunction field effect transistors. IEEE Transactions on Power Electronics 32 (11), pp.8743-8750. (10.1109/TPEL.2016.2643499)
- Kuball, M. et al., 2007. Time-resolved temperature measurement of AlGaN/GaN electronic devices using micro-raman spectroscopy. IEEE Electron Device Letters 28 (2), pp.86-89. (10.1109/LED.2006.889215)
- Lee, L. Y. et al., 2019. Investigation of MOVPE-grown zincblende GaN nucleation layers on 3C-SiC/Si substrates. Journal of Crystal Growth 524 125167. (10.1016/j.jcrysgro.2019.125167)
- Lee, L. Y. et al., 2019. Investigation of stacking faults in MOVPE-grown zincblende GaN by XRD and TEM. Journal of Applied Physics 125 105303. (10.1063/1.5082846)
- Leigh, W. et al. 2023. Monitoring of the initial stages of diamond growth on aluminum nitride using in situ spectroscopic ellipsometry. ACS Omega 8 (33), pp.30442-30449. (10.1021/acsomega.3c03609)
- Mandal, S. et al. 2017. Surface zeta potential and diamond seeding on gallium nitride films. ACS Omega 2 (10), pp.7275-7280. (10.1021/acsomega.7b01069)
- Mandal, S. et al. 2019. Thick, adherent diamond films on AlN with low thermal barrier resistance. ACS Applied Materials and Interfaces 11 (43), pp.40826-40834. (10.1021/acsami.9b13869)
- Rae, K. et al., 2017. InGaN µLEDs integrated onto colloidal quantum dot functionalized ultra-thin glass. Optics Express 25 (16), pp.19179-19184. (10.1364/OE.25.019179)
- Riedel, G. J. et al., 2009. Reducing thermal resistance of AlGaN/GaN electronic devices using novel nucleation layers. IEEE Electron Device Letters 30 (2), pp.103-106. (10.1109/LED.2008.2010340)
- Riedel, G. et al., 2008. Nanosecond timescale thermal dynamics of AlGaN/GaN electronic devices. IEEE Electron Device Letters 29 (5), pp.416-418. (10.1109/LED.2008.919779)
- Sarua, A. et al., 2007. Thermal boundary resistance between GaN and substrate in AlGaN/GaN electronic devices. IEEE Transactions of Electron Devices 54 (12), pp.3152-3158. (10.1109/TED.2007.908874)
- Shu, R. et al., 2025. Beyond transmission electron microscopy imaging: atom probe tomography reveals chemical inhomogeneity at stacking fault interfaces in InGaN/GaN light-emitting diodes. Materialia 40 102417. (10.1016/j.mtla.2025.102417)
- Spiridon, B. F. et al., 2021. Method for inferring the mechanical strain of GaN-on-Si epitaxial layers using optical profilometry and finite element analysis. Optical Materials Express 11 (6), pp.1643-1655. (10.1364/OME.418728)
- Sun, C. et al., 2020. Thin film gallium nitride (GaN) based acoustofluidic tweezer: modelling and microparticle manipulation. Ultrasonics 108 106202. (10.1016/j.ultras.2020.106202)
- Sun, C. et al., 2020. Gallium nitride: a versatile compound semiconductor as novel piezoelectric film for acoustic tweezer in manipulation of cancer cells. IEEE Transactions on Electron Devices 67 (8), pp.3355-3361. (10.1109/TED.2020.3002498)
- Tang, F. et al., 2018. Nanoscale structural and chemical analysis of F-implanted enhancement-mode InAlN/GaN heterostructure field effect transistors. Journal of Applied Physics 123 (2) 024902. (10.1063/1.5006255)
- Vacek, P. et al., 2021. Defect structures in (001) zincblende GaN/3C-SiC nucleation layers. Journal of Applied Physics 129 (15) 155306. (10.1063/5.0036366)
- Wade, T. et al., 2023. MOVPE studies of zincblende GaN on 3C-SiC/Si(0 0 1). Journal of Crystal Growth 611 127182. (10.1016/j.jcrysgro.2023.127182)
- Wadsworth, A. et al., 2023. GaN-based cryogenic temperature power electronics for superconducting motors in cryo-electric aircraft. Superconductor Science and Technology 36 (9) 094002. (10.1088/1361-6668/ace5e7)
- Waller, W. M. et al., 2015. Interface state artefact in long gate-length AlGaN/GaN HEMTs. IEEE Transactions of Electron Devices 62 (8), pp.2464-2469. (10.1109/TED.2015.2444911)
- Waller, W. M. et al., 2016. Subthreshold Mobility in AlGaN/GaN HEMTs. IEEE Transactions on Electron Devices 63 (5), pp.1861-1865. (10.1109/TED.2016.2542588)
- Wallis, D. et al. 2001. Measurement of III-V quaternary composition using X-ray diffraction. IEE Proceedings Optoelectronics 148 (2), pp.97-100. (10.1049/ip-opt:20010442)
- Wallis, D. , Watson, A. and Mo, N. 1996. Cardiac neurones of automatic ganglia. Microscopy Research and Technique 35 (1), pp.69-79. (10.1002/(SICI)1097-0029(19960901)35:1<69::AID-JEMT6>3.0.CO;2-N)
- Wiles, A. A. et al., 2020. A poly(urethane)-encapsulated benzo[2,3-d:6,7-d’]diimidazole organic down-converter for green hybrid LEDs. Materials Chemistry Frontiers 4 (3), pp.1006-1012. (10.1039/C9QM00771G)
- Xiu, H. et al., 2023. Polarity determination of crystal defects in zincblende GaN by aberration-corrected electron microscopy. Journal of Applied Physics 133 105302. (10.1063/5.0138478)
- Xu, X. et al., 2025. Effect of buffer layer thickness on recombination in zincblende InGaN/GaN quantum wells. Journal of Physics D: Applied Physics 58 (47) 475101. (10.1088/1361-6463/ae1d8d)
- Xu, X. et al., 2025. Point defect luminescence associated with stacking faults in magnesium doped zincblende GaN. Journal of Applied Physics 137 (23) 235301. (10.1063/5.0274599)
- Yang, H. et al., 2023. A cross-linkable, organic down-converting material for white light emission from hybrid LEDs. Journal of Materials Chemistry C Materials for optical and electronic devices 11 (29), pp.9984-9995. (10.1039/D2TC05139G)
- Yi, L. et al., 2018. Effect of growth temperature and V/III-ratio on the surface morphology of MOVPE-grown cubic zincblende GaN. Journal of Applied Physics 124 105302.
- Yin, Y. et al., 2022. Fabrication of semi-polar (11-22) GaN V-groove MOSFET using wet etching trench opening technique. IEEE Electron Device Letters 43 (10), pp.1641-1644. (10.1109/LED.2022.3203633)
- Zaidi, Z. H. et al., 2018. Effects of surface plasma treatment on threshold voltage hysteresis and instability in metal-insulator-semiconductor (MIS) AlGaN/GaN heterostructure HEMTs. Journal of Applied Physics 123 (18) 184503. (10.1063/1.5027822)
Conferences
- Ashley, T. et al., 2007. Indium antimonide based quantum well FETs for ultra-high speed electronics. Presented at: 64th Device Research Conference State College, PA 26-28 June 2006. , pp.201. (10.1109/DRC.2006.305056)
- Ashley, T. et al., 2006. Indium antimonide based technology for RF applications. Presented at: Compound Semiconductor Integrated Circuit Symposium San Antonio, TX 12-15 Nov 2006. (10.1109/CSICS.2006.319918)
- Ashley, T. et al., 2010. High-performance InSb based quantum well field effect transistors for low-power dissipation applications. Presented at: 2009 IEEE International Electron Devices Meeting (IEDM) Baltimore, MD, USA 7-9 December 2009. 2009 IEEE International Electron Devices Meeting (IEDM). IEEE. , pp.1. (10.1109/IEDM.2009.5424207)
- Benakaprasad, B. et al. 2017. Design and performance comparison of various terahertz microstrip antennas on GaN-on-low resistivity silicon substrates for TMIC. Presented at: Microwave Conference (APMC), Asia-Pacific New Delhi, India 5-9 Dec 2016. Proceedings of the Asia-Pacific Microwave Conference 2016. IEEE(10.1109/APMC.2016.7931368)
- Benakaprasad, B. et al. 2016. Terahertz microstrip single patch antenna technology on GaN-on-Low resistivity silicon substrates for TMIC. Presented at: IET Colloquium on Antennas, Wireless and Electromagnetics Glasgow, UK 26 May 2016.
- Benakaprasad, B. et al. 2016. Terahertz monolithic integrated circuits (TMICs) array antenna technology on GaN-on-Low resistivity silicon substrates. Presented at: 41st International Conference on Infrared, Millimeter, and Terahertz waves (IRMMW-THz), Copenhagen, Denmark 25-30 Sep 2016. 2016 41st International Conference on Infrared, Millimeter, and Terahertz waves (IRMMW-THz),. IEEE(10.1109/IRMMW-THz.2016.7758488)
- Chatterjee, I. et al., 2016. Impact of buffer charge on the reliability of carbon doped AlGaN/GaN-on-Si HEMTs. Presented at: 2016 IEEE International Reliability Physics Symposium (IRPS) Pasadena, CA, USA 17-21 April 2016. 2016 IEEE International Reliability Physics Symposium (IRPS). IEEE. , pp.4A41-4A45. (10.1109/IRPS.2016.7574529)
- Datta, S. et al., 2005. 85nm gate length enhancement and depletion mode InSb quantum well transistors for ultra high speed and very low power digital logic applications. Presented at: IEEE International Electron Devices Meeting Washington DC 5 Dec 2005. Electron Devices Meeting, 2005. IEDM Technical Digest. IEEE International. IEEE. (10.1109/IEDM.2005.1609466)
- Dyer, D. et al., 2025. Broadly tunable cubic phase InGaN/GaN quantum wells grown by metal-organic chemical vapor deposition.. Presented at: OPTO: Gallium Nitride Materials and Devices XX San Francisco, CA, USA 25-31 January 2025. Published in: Fujioka, H. , Morkoc, H. and Schwarz, U. T. eds. Proceedings Volume 13366, Gallium Nitride Materials and Devices XX. SPIE. (10.1117/12.3039278)
- Eblabla, A. et al. 2017. Passive components technology for THz-Monolithic Integrated Circuits (THz-MIC). Presented at: 18th International Radar Symposium (IRS), 2017 Prague, Czech Republic 28-30 June 2017. Radar Symposium Conference Proceedings. , pp.1-7. (10.23919/IRS.2017.8008166)
- Eblabla, A. et al. 2016. High frequency active and passives devices using GaN on low resistivity silicon. Presented at: ARMMS RF & Microwave Society Conference Milton Common Nr Thame, UK 18-19 Apr 2016.
- Elgaid, K. et al. 2016. MMIC-compatible microstrip technology for GaN-HEMTs on low resistivity silicon substrate. Presented at: International Workshop on Nitride Semiconductors (IWN 2016) Orlando, FL, USA 2-7 Oct 2016.
- Jamil, S. et al., 2016. Standby person for electrical tasks and rescue guidelines for electrical incident victims. Presented at: Petroleum and Chemical Industry Technical Conference (PCIC) Philadelphia, PA, USA 19-22 Sep 2016. IEEE(10.1109/PCICON.2016.7589220)
- Janssen, J. et al., 2009. X-Band GaN SPDT MMIC with over 25 watt linear power handling. Presented at: European Microwave Integrated Circuit Conference, 2008 Amsterdam, The Netherlands 27-28 October 2009. 2008 European Microwave Integrated Circuit Conference. IEEE(10.1109/EMICC.2008.4772261)
- Miaja, P. F. et al., 2016. Modelling the closely-coupled cascode switching process. Presented at: 2016 IEEE Energy Conversion Congress and Exposition (ECCE) Milwaukee, WI 18-22 September 2016. 2016 IEEE Energy Conversion Congress and Exposition (ECCE). IEEE(10.1109/ECCE.2016.7855268)
- Radosavljevic, M. et al., 2008. High-performance 40nm gate length InSb p-channel compressively strained quantum well field effect transistors for low-power (VCC=0.5V) logic applications. Presented at: IEEE International Electron Devices Meeting San Francisco, CA 15-17 Dec 2008. (10.1109/IEDM.2008.4796798)
- Roff, C. et al., 2018. Utilization of waveform measurements for degradation analysis of AlGaN/GaN HFETs. Presented at: ARFTG 70th Microwave Measurement Symposium Tempe, AZ, USA 27-30 November 2007. 2007 70th ARFTG Microwave Measurement Conference (ARFTG). IEEE. (10.1109/ARFTG.2007.8376173)
- Shi, C. et al., 2024. A circuit for evaluating GaN HEMT dynamic Rds(on) at cryogenic temperatures. Presented at: 9th Southern Power Electronics Conference (SPEC) Brisbane, Australia 2-5 December 2024. Proceedings of 9th Southern Power Electronics Conference. IEEE. , pp.1-6. (10.1109/spec62217.2024.10893110)
- Uren, M. et al., 2006. Control of Short-Channel Effects in GaN/AlGaN HFETs. Presented at: 1st European Microwave Integrated Circuits Conference Manchester, UK 10-13 Sept 2006. 2006 European Microwave Integrated Circuits Conference. IEEE. , pp.65-65. (10.1109/EMICC.2006.282751)
- Wallis, D. 2006. Class F at class B temperatures is it time for a change?. Presented at: Conference Record of the 2006 IEEE International Symposium on Electrical Insulation, 2006 Toronto, Ont., Canada 11-14 June 2006. (10.1109/ELINSL.2006.1665243)
- Wallis, D. 2016. The hazards of risk assessment. Presented at: Electrical Safety Workshop (ESW) Jacksonville, FL, USA 6-11 March 2016. (10.1109/ESW.2016.7499706)
Research
ID | Title | Funder | Dates | Value | PI/CoI | ||
EP/R01146X/1 |
| EPSRC | 2/18 –1/21 | £493k | PI | ||
EP/R03480X/1 | 'Hetero-print': A holistic approach to transfer-printing for heterogeneous integration in manufacturing | EPSRC | 6/18 – 5/23 | £5.5M | CoI | ||
EP/P00945X/1 | Integrated GaN-Diamond Microwave Electronics: From Materials, Transistors to MMICs | EPSRC | 1/17 - 12/21 | £4.3M | CoI | ||
EP/N017927/1 | Integration of RF Circuits with High Speed GaN Switching on Silicon Substrates | EPSRC | 5/16 - 4/19 | £2.4M | CoI | ||
EP/P03036X/1 | Vertical cubic GaN LEDs on 150mm 3C-SiC substrates | IUK | 2/17 - 7/18 | £208k | PI | ||
EP/N01202X/2 | EPSRC Manufacturing Fellowship in Gallium Nitride | EPSRC | 3/16 - 2/21 | £1.3M | PI | ||
103446 | GaNSense | IUK | 10/17-12/18 | £306k | CoI | ||
EP/S01005X/1 | Non-linear (large signal) Millimetre-wave Devices, Circuits and Systems On-Wafer Characterization Facility | EPSRC | 10/18 - 9/19 | £1.4M | CoI | ||
EEF6084 | Energy Entrepreneurs grant | BEIS | 10/18 - 9/20 | £690k | PI |
Biography
I currently hold a join chair in Compound semiconductors between the Universities of Cardiff and Cambridge and I am also an EPSRC Manufacturing fellow. Before taking up my current academic position I was employed by Plessey Semiconductors and was responsible for setting up their GaN growth capability and the technology transfer of the GaN on Si growth technology that they aquired from the University of Cambridge to enable the launch of their GaN on Si LED products. Prior to this I worked for QinetiQ Plc for 14 years and was technical lead for their GaN growth and characterisation capability. This role was largely focused on the development of GaN based RF devices. I recieved my PhD in Microstructural Physics from the University of Cambridge.
Supervisions
I am interested in supervising PhD students in the area of
- GaN growth
- GaN characterisation
- GaN devices
Contact Details
[email protected]
+44 29208 79065
Queen's Buildings - South Building, Room Room S/1.08, 5 The Parade, Newport Road, Cardiff, CF24 3AA
+44 29208 79065
Queen's Buildings - South Building, Room Room S/1.08, 5 The Parade, Newport Road, Cardiff, CF24 3AA
Research themes
Specialisms
- Compound semiconductors