Details of Grant 

EPSRC Reference:	GR/L56725/01
Title:	THEORY OF TRANSPORT PHENOMENA IN LARGE-BANDGAP SEMICONDUCTORS
Principal Investigator:	Ridley, Professor BK
Other Investigators:	Babiker, Professor M
Researcher Co-Investigators:
Project Partners:
Department:	Physics
Organisation:	University of Essex
Scheme:	Standard Research (Pre-FEC)
Starts:	01 September 1997	Ends:	31 August 2000	Value (£):	170,924
EPSRC Research Topic Classifications:	Materials Characterisation
EPSRC Industrial Sector Classifications:	Electronics
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Panel History:
Summary on Grant Application Form
The favourable properties of wide-gap semiconductors for visible-light emission and high-power microwave devices are now being exploited world-wide, and our research aims to provide theoretical underpinning for optimising device performance. Detailed numerical simulations require basic input of the physics of electrons and phonons and their interactions in both bulk and quantum-well devices and our aim is to provide that basic input. We will give an account of electron, hole and phonon quantum confinement in heterostructures and dynamically screened scattering and well-capture rates of charge carriers using hybrid-phonon theory. We will also develop a theory of hot-phonon effects, and of LO-phonon lifetime in the light of availability of improved theoretical data on phonon bandstructure. One of the major areas of solid-state physics where the understanding is poor is very high field transport and breakdown in large bandgap materials where carriers are hot enough to populate the whole of the first brillouin zone and there is the possibility of Wannier-Stark states forming. We will describe transport and breakdown in this regime and associated instabilities and the possibility of Thz emission. Our methodology will mix numerical and analytical techniques and the use of approximate models like lucky-drift theory for breakdown and statistical screening for charged-impurity scattering in semiconductors. An important concern will be to describe the effect of multi-subband occupancy on screening and coupled-mode effects in quantum well heterostructures, the results of which will have direct application to the performance of high power FETs. We will examine the consequences of the strong piezoelectricity of many of these materials regarding scattering rates and the acoustoelectric effect.. We expect to research to be directly relevant to the optimisation of the performance of existing devices and to stimulate the invention of new devices.
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Organisation Website:	http://www.sx.ac.uk