Browsing by Author "Mindil, Ahmed"

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    Investigation of contact edge effects in the channel of planar Gunn diodes
    (IEEE, 2019-11-26) Mindil, Ahmed; Dunn, G. M.; Khalid, Ata; Oxley, C. H.
    The effect of the edge of the channel on the operation of Planar Gunn diodes has been examined using Monte Carlo simulations. High fields at the corner of the anode contact are known to cause impact ionization and consequent electroluminescence, but our simulations show that the Gunn domains are attracted to these corners, perturbing the formation of the domains which can lead to chaotic dynamics within the rest of the channel leading to uneven heating and reduced RF output power. We show how novel shaping of the electrical contacts at the ends of the channel reduces the attraction and restores the domain wave-fronts for good device operation.
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    Investigation of high-frequency fine structure in the current output of shaped contact planar gunn diodes
    (IEEE, 2020-04-08) Mindil, Ahmed; Dunn, Geoffrey; Khalid, Ata; Oxley, Chris H.
    A novel gallium arsenide (GaAs) planar Gunn diode design with shaped anode and cathode contacts using Monte Carlo simulations has been shown to produce significantly higher frequency fine structure components in the output waveform than the natural transit time frequency of the diode. We have investigated devices without a feed- back potential and devices with a feedback potential (in the delayed mode) and have shown 350-GHz fine structure frequency components in a device with a nominal transit time frequency of 70 GHz is possible. This is the first observation of such stable repeating high-frequency components in a Gunn diode, giving potential for very high-frequency power generation and other wave-shaping applications.
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    Investigation of THz frequency shaped anode planar Gunn diodes operating in delayed mode
    (IEEE, 2020-10-06) Mindil, Ahmed; Dunn, Geoffrey; Khalid, Ata; Oxley, Chris
    A novel planar design of Gunn diode with a shaped anode contact, utilizing Monte Carlo simulations, has been shown to have produced 0.3 THz frequency current output when operated in delayed mode. Two novel anode designs are investigated here, one with two fixed distances, and the other with three fixed distances between the cathode and anode electrodes. The corresponding waveforms generated, show two and three current peaks respectively. The work suggests high frequency and novel wave-shaping applications are possible in such devices.