Professor John David
Departmental Director of Admissions
Tel: +44 (0)114 22 25185
Research Group: Semiconductor Materials & Devices
I obtained my B.Eng. and Ph.D. degrees in Electronic Engineering from the University of Sheffield in 1979 and 1983, respectively. After that, I undertook a number of postdoctoral positions within the Department of Electronic & Electrical Engineering at Sheffield eventually managing the characterisation activities of the SERC Centre for III–V Semiconductors. In 2001 I left to join Marconi Optical Components, Caswell before returning the following year as a Senior Lecturer. In 2004 I became Professor of Semiconductor Materials and Devices, and between 2009 to 2013 served as Head of Department. Between 2002 -2004 I was a IEEE LEOS Distinguished Lecturer and I am currently a Fellow of the IEEE and IET.
My research is focussed in two areas; i) on the characterisation of III-V semiconductor materials and devices, especially that containing Bismuth and ii) on the understanding and development of avalanche photodiodes. The addition to Bismuth offers a possible route to extend the wavelength of many optical structures such as photodiodes and solar cells. I use characterisation techniques such as X-ray double crystal diffraction and photoluminescence to study semiconductor structures containing bulk and quantum wells of GaAsBi and , and then correlate this to current-voltage, capacitance-voltage and photocurrent spectra of fabricated devices.
I also study how under very high electric-fields, electrons and holes in a semiconductor gain energy and create further carriers through a process of impact ionisation. This process can lead to destructive breakdown in power electronic devices but can also be utilised to amplify weak optical signals, giving rise to avalanche photodiodes (APDs). I study the theory behind the ionisation process via different modelling techniques and also look experimentally at the ionisation coefficients in different semiconductor materials and device structures. The aim of my research is to develop APDs capable of operating at very high speeds for next generation telecommunication networks and also APDs that are very sensitive.