Advanced Gunn Diode as High Power Terahertz Source for a Millimetre Wave High Power Multiplier F. Amir a , C. Mitchell a , N. Farrington b and M. Missous a a M&N Group, School of E&EE, University of Manchester, M60 1QD, UK b e2v Technologies (UK) Plc, Carholme Rd, Lincoln, LN1 1SF, UK ABSTRACT An advanced step-graded Gunn diode is reported, which has been developed through joint modelling-experimental work. The ~ 200 GHz fundamental frequency devices have been realized to test GaAs based Gunn oscillators at sub-millimetre wave for use as a high power (multi mW) Terahertz source in conjunction with a mm-wave multiplier, with novel Schottky diodes. The epitaxial growth of both the Gunn diode and Schottky diode wafers were performed using an industrial scale Molecular Beam Epitaxy (V100+) reactor. The Gunn diodes were then manufactured and packaged by e2v Technologies (UK) Plc. Physical models of the high power Gunn diode sources, presented here, are developed in SILVACO. Keywords: Gunn diode, physical modelling, mm-wave multiplier, Schottky varactor, security imaging, sub-millimetre imaging. 1. INTRODUCTION Gunn and mixer diodes will “power” future THz security imaging systems. The Gunn diode’s low phase noise, moderate output power, reliable long-term operation and relatively low cost makes it ideal for millimetre-wave imaging systems. This work expands on a previously developed 2D rectangular model [1, 2, 4] developed for an advanced step-graded GaAs-AlGaAs Gunn diode with hot electron injector [5] commercially manufactured in volume by e2v Technologies (UK) Plc. for use in 77GHz automotive Autonomous Cruise Control (ACC) systems. The tight specifications placed on parameters such as RF output power, applied voltage controlled frequency tuning range and the oscillation frequency’s temperature dependence demand exquisite control over the materials composition and thicknesses. These parameters are all highly dependant on hot-electron injector composition, especially carrier concentration in the injector’s doping spike [3, 6, 7]. To compliment experimentally obtained data and perform a sensitivity analysis on the effects of variation in epitaxial composition, especially carrier concentration in the doping spike and transit region, predictive physical models, using SILVACO, have been developed. After successful development of 77GHz (second harmonic) and 100 GHz fundamental models, the computational work was extended to increase the device operating frequency to ~ 200 GHz fundamental in this work. The main motivation behind this work was to test whether GaAs based Gunn oscillators operating at sub-millimetre waves can be realized. These high frequencies have, hitherto, been outside the capabilities of conventional GaAs Gunn diodes. The development of such devices, when used with multipliers as a high power terahertz source, should permit much needed components for use in sub-millimetre wave imaging applications. The joint modelling-experimental work reported here will also provide a sound foundation for future high-frequency high-power multiplier source development in the Terahertz regime and with output powers in the mW range. 2. SIGNAL GENERATION The THz frequencies considered (up to 600 GHz) are to be generated in a two-stage module. The initial frequency source is to be provided by the novel high frequency Gunn diodes described in detail in this paper. The output from these diodes is then to be coupled into a multiplier module. The realisation of high power Gunn diodes operating at higher frequency, enable THz generation with a single stage multiplier module. A single stage multiplier potentially reduces Invited Paper Millimetre Wave and Terahertz Sensors and Technology II, edited by Keith A. Krapels, Neil A. Salmon, Proc. of SPIE Vol. 7485, 74850I · © 2009 SPIE · CCC code: 0277-786X/09/$18 · doi: 10.1117/12.830296 Proc. of SPIE Vol. 7485 74850I-1