MEng, PhD (Warwick), MIET, MIEEE, FHEA
My main research interest is in developing new electronic devices that can work in the ‘harsh’ environment, where reliability and efficiency must be maintained despite operating in extreme surroundings. Harsh environment applications include space, oil and gas exploration, aerospace or electric vehicles, where temperatures range from the very hot to the very cold, or where great vibration or shock, radiation, humidity or electromagnetic interference are an issue.
|I am working to develop a range of power electronic devices that can work in the harsh environment. These use a novel silicon on silicon carbide (Si/SiC) substrate that exploits the advantages of each of the semiconductors. A thin film of silicon is a reliable and highly efficient device layer for electronics at low-medium voltages (<600V). It also allows for easy, well established fabrication techniques to be used. The SiC helps to manage self-heating, its high thermal conductivity removing the heat from the silicon top layer, with the aim to keep the temperature inside the device as close to that outside it.|
I am principal investigator on three projects that look to develop Si/SiC solutions:
Generously funded for five years in March 2012 by the Royal Academy of Engineering, this project has focussed on establishing materials solutions for the harsh environment. The Si/SiC concept, along with the methodology for creating these wafers have been developed in this project, and will be used in the following two projects. This project has also been responsible for developing Si/SiC simulations, which have led to an optimised and subsequently patented device layout. The NICHE project is also involved in developing ideas for Ge/SiC and Si/Diamond.
SaSHa is the largest ever Si/SiC project and will begin in February 2016, funded for two years by the EU’s Horizon 2020 programme. Concentrating on the development of power electronics devices specifically for Space applications, the devices will be designed to withstand temperatures as high as 300°C and as low as -150°C, and in high radiation conditions. The consortium will be led at Warwick who will produce the Si/SiC devices in their unique cleanroom facility. UK SME, Cambridge Microelectronics, will carry out extensive simulations in order to optimise a design layout. The Tyndall Institute in Ireland will produce the novel wafer bonded Si/SiC material, while the Catholic University of Leuven (UCL) will carry out radiation modelling and testing. Thales Alenia Space UK will play a major role in shaping the characteristics of the devices.
Beginning November 2015, this £125k EPSRC will for two years look to develop Si/SiC power devices for downhole applications with project partners Halliburton and TT Electronics. With a temperature gradient beneath the surface of around 25°C/km, the ambient conditions can exceed 225°C in the deepest wells, while coping at the same time with extreme vibration, pressure, and corrosive liquids and gases. Maintaining reliability in this environment is a significant challenge, especially given the often quoted figure for downtime on an offshore rig being more than $1M per day to the drilling company.
My team is supporting Thales Alenia Space UK in an exciting project to create a satellite delivery vehicle powered from the ground via microwave beamed propulsion. Such a system would do away with propellant, achieving a single-stage-to-orbit system that can be reused hundreds of times. An extensive overview of the project is available here.
Warwick's interest lies in the development of a power electronics solution, a rectifying antenna (rectenna), that will convert the incoming high frequency, high power microwave signal into DC power usable on board the vehicle. This solution requires a new diode that can cope with these conflicting demands at high temperature given the inevitable wasted power. We are therefore investigating the ability of high power, wide bandgap semiconductors (SiC and GaN) to operate in the GHz range, using simulation tools to design a novel device layout, before implementing the design in our cleanroom for a prototype.
I have worked extensively in other research fields including SiC and GaN power electronics, on the modelling of metal/semiconductor Schottky diodes and on energy harvesting techniques using rectennas devices.
My work on modelling Schottky diodes has helped to explain curious effects, 'inhomogeneities', witnessed in the turn-on characteristics of these devices, such as decreasing ideality factor, increasing barrier height and, in particularly extensive double bumps in the log(I)-V plots. My 2013 Journal of Applied Physics paper describes how the best known theory into metal-semiconductor inhomogeneity can be developed into a technique that can model real experimental data, so establishing a method to quantify the homogeneity of a diode.
In collaboration with Imperial College, work was carried out on another rectenna application, this time for solar energy harvesting. Based on a scaled-down version of your radio or T.V. antenna, nano-scaled gold antennae couple with the infra-red, or visual spectrum setting up a small electric field across the metal-semiconductor interface. Our work in this area was published in the first ever article to appear in the journal MRS Energy & Sustainability: A Review Journal.
The Engineering Department at the University of Warwick is renowned for its research activity into SiC Power devices. With a unique clean room facility dedicated to SiC power device fabrication, significant research effort is being invested into bringing these high power density, high frequency and high temperature devices to market. I have an interest in SiC Schottky and PiN diodes, characterising Fermi-level pinning, and temperature-based effects. I am also interedsted in characterising SiC MOSFETS and other devices at cryogenic temperatures down below 20K.
Chunwa Chan (Si/SiC Power Devcies)
Yegi Bonyadi (SiC Power Devices)
Oliver Vavasour (Dielectrics for III-V devices)
MSc by Research:
Naiwu Yuan (SiC Applications)
MSc by Research:
Han Chen (SiC Cryogenic Performance)
GaN Power Electronics: