Professor and Director of Research
BSc Imperial College
PhD University of Cambridge
MA University of Oxford
Hon DSc University of Leicester
Gallium Nitride, Electron Microscopy and Aerospace
My research is broad and covers three main areas: gallium nitride materials and devices; advanced electron microscopy; and high-temperature aerospace materials.
Gallium-nitride materials and devices
Gallium nitride (GaN) is probably the most important semiconductor material since silicon. It emits brilliant light as well as being a key material for next-generation transistors. The Cambridge Centre for Gallium Nitride in the Department has world-class growth and characterization facilities. On the same site we have a six-wafer MOCVD growth system, plus a range of world-class characterization equipment, including advanced electron microscopy and analysis, high-resolution X-ray diffraction, atomic-force microscopy, photoluminescence mapping, etc. My group of about 20 works at the cutting edge of GaN research worldwide. Our research goes from fundamental studies through to applications in LEDs and lasers, including next-generation solid-state lighting and UV LEDs for purifying water in the developing world.
Advanced electron microscopy and analysis
We are developing and applying a range of advanced electron microscopy techniques. For example, we have pioneered energy-filtered secondary-electron imaging in scanning electron microscopy for the mapping of dopants in silicon and other semiconductor devices. We are applying high-resolution electron microscopy, electron-energy-loss spectroscopy and electron holography to gallium nitride based structures in particular. An aberration-corrected and monochromated electron microscope will shortly be delivered, which together with a new dual-beam focused-ion-beam instrument will keep electron microscopy at Cambridge as a world-class centre (see www.msm.cam.ac.uk/hrem).
High-temperature aerospace materials
The Department contains the Rolls-Royce University Technology Partnership in Advanced Materials. We are designing and developing higher-temperature advanced alloys that will improve the efficiency of gas-turbine engines, resulting in reduced fuel consumption and reduced emissions.
|3-D atom-probe image of InGaN/GaN quantum wells. Each dot represents a single atom: light blue is gallium and orange is indium|
- Zhu D, Wallis DJ and Humphreys CJ, “Prospects of III-nitride optoelectronics grown on Si”, Reports on Progress in Physics, 76 (2013) 106501.
- Davies MJ, Badcock TJ, Dawson P, Kappers MJ, Oliver RA and Humphreys CJ, “High excitation carrier density recombination dynamics of InGaN/GaN quantum well structures: Possible relevance to efficiency droop”, Appl. Phys. Lett.,102 (2013) 022106.
- Radtke G, Couillard M, Botton GA, Zhu D and Humphreys CJ, “Structure and chemistry of the Si(111)/AlN interface”, Appl. Phys. Lett., 100(2012) 011910.
- Hammersley S, Watson-Parris D, Dawson P, Godfrey MJ, Badcock TJ, Kappers MJ, McAleese C, Oliver RA and Humphreys CJ, “The consequences of high injected carrier densities on carrier localization and efficiency droop in InGaN/GaN quantum well structures”, J. Appl. Phys., 111(2012) 083512.