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Details of Grant 

EPSRC Reference: GR/J50668/01
Principal Investigator: Childs, Dr P
Other Investigators:
Researcher Co-Investigators:
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Department: Electronic, Electrical and Computer Eng
Organisation: University of Birmingham
Scheme: Standard Research (Pre-FEC)
Starts: 01 August 1993 Ends: 31 July 1996 Value (£): 98,003
EPSRC Research Topic Classifications:
Electronic Devices & Subsys.
EPSRC Industrial Sector Classifications:
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Summary on Grant Application Form
1. To develop a hybrid Monte Carlo/iterative method of solving the Boltzmann transport equation.2. To use this method to study hot carrier transport in APDs and HEMTs and to design new high performance structures.3. In conjunction with experiment to determine fundamental parameters of hot electron transport.Progress:The hybrid solution of the Boltzmann transport equation has now been developed. Software problems relating to the interface between the Monte Carlo solution and the iterative solution have been solved and the programme will be continually developed throughout the duration of the project. Initial Monte Carlo studies have been undertaken to determine the effect of the low energy band structure on carrier transport across the interface of III-V heterostructures. The role of the soft threshold characteristic in determining impact ionisation rates in heterostructures is presently being studied. Modification of the ratio of the impact ionisation rate of electrons to that of holes by dead space engineering has been proposed as technique for reducing noise in APDs. We have used the hybrid technique to study the transition from dead space to spatial homogeneity of the distribution function. As part of this work we have observed and physically explained [1] the unexpected form of the high energy tail of the distribution. Experimental studies of hot carrier transport parameters have begun with the fabrication of novel bipolar structures by the EPSRC III-V semiconductor facility at Sheffield University. Initial experiments suggest that the devices are operating as expected. However, an unforeseen leakage current, probably resulting from light emission, has to date limited the range of measurements. It is believed that this problem can be eliminated by band structure engineering and a new design will shortly be provided to Sheffield. One advantage of iterative solutions of the Boltzmann transport equation is that by comparison with Monte Carlo it is relatively easy to include electron - electron scattering in the simulation. As a by-product of this work the hybrid technique has been used to study hot carrier generation by electron - electron scattering [2]. Results from this work suggest that impact ionisation and gate currents may persist in devices operating at very low supply voltages. [1] C. C. C. Leung and P. A. Childs, Appl. Phys. Lett. 66 (2) 1 (1995).[2] P. A. Childs and C. C. C. Leung, Electronics Lett. 31 (2) 139 (1995).
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Organisation Website: http://www.bham.ac.uk