The length of the transit region of a Gunn diode determines the natural frequency at which it operates in fundamental modethe shorter the device, the higher the frequency of operation. The long-held view on Gunn diode design is that for a functioning device the minimum length of the transit region is about 1.5μm, limiting the devices to fundamental mode operation at frequencies of roughly 60 GHz. Study of these devices by more advanced Monte Carlo techniques that simulate the ballistic transport and electron-phonon interactions that govern device behaviour, offers a new lower bound of 0.5μm, which is already being approached by the experimental evidence that has shown planar and vertical devices exhibiting Gunn operation at 600nm and 700nm, respectively. The paper presents results of the first ever THz submicron planar Gunn diode fabricated in In0.53Ga0.47As on an InP substrate, operating at a fundamental frequency above 300 GHz. Experimentally measured rf power of 28 µW was obtained from a 600 nm long ×120 µm wide device. At this new length, operation in fundamental mode at much higher frequencies becomes possible -the Monte Carlo model used predicts power output at frequencies over 300 GHz.

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(2013) Impact ionisation electroluminescence in planar GaAs-based heterostructure gunn diodes: spatial distribution and impact of doping non-uniformities. Journal of Applied Physics, 113 (12).

. (2017) Thermal profiles within the channel of planar gunn diodes using micro-particle sensors. IEEE Electron Device Letters, 38(9), pp. 1325-1327. (doi:10.1109/LED.2017 This is the author's final accepted version.There may be differences between this version and the published version. You are advised to consult the publisher's version if you wish to cite from it.http://eprints.gla.ac.uk/146304/ Abstract-The paper describes the use of a novel microparticle sensor (∼3 µm diameter) and infra-red (IR) microscopy to measure the temperature profile within the active channel (typically 3 µm length and 120 µm width) of planar Gunn diodes. The method has enabled detailed temperature measurements showing an asymmetrical temperature profile along the active width of these devices. The asymmetrical temperature profile suggests a similar behaviour in the channel current density, which may contribute to the lower than expected RF output power.