Browsing by Author "Van Zyl, Robert Ryk"

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    The optimisation of mm-Wave GaAs Gunn diodes using a parallel implementation of the Monte Carlo particle simulation technique
    (Stellenbosch : Stellenbosch University, 2006-12) Van Zyl, Robert Ryk; Perold, W. J.; Botha, R.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: The principal research objective is the optimisation of the output power of GaAs Gunn diodes in the mm-wave spectrum. Specifically, the optimisation of Gunn diodes operating at 94GHz is investigated due to its relevance to current automotive and military precision radar applications. A novel multi-domain Gunn diode with multiple hot-electron launchers is proposed and evaluated. This concept has been successfully applied to a double-domain Gunn diode. Further avenues of optimisation that have been incorporated into the design are notch doping and grading of the active layer doping profile. Output power in the region of 160m W at 2% efficiency can be expected from these diodes. This is far superior to current state-of-the-art GaAs Gunn diodes which are capable of around 90m W at 94GHz. Although it has not been investigated, the optimised diode should benefit from the same advantages of a single domain hot-electron launcher diode. These advantages are reduced sensitivity to temperature and bias variations, improved tum-on characteristics and noise performance. The design has been optimised using a novel parallel implementation of the Monte Carlo particle simulation technique. A cluster of personal computers, linked via a dedicated high-speed gigabit network, has been established. This renders a cost-effective super computer. The simulation model has been verified rigorously by comparing simulation results with real-life scenarios. Thermal effects are incorporated into the overall Monte Carlo model. Temperature is determined with fine grid-resolution throughout the device and not assumed constant. This enables us to investigate the influence of graded doping profiles on device performance in. more detail, and renders a more realistic model of high temperature Gunn diodes.