Silicon baritt diodes as millimetre wavelength oscillators

Abstract

The capabilities of the silicon baritt device in the millimetre wavelength range are presented. Analytical treatment shows that the positive resistance of the forward-biased zone is a fundamental limitation of the device operation. An exact large-signal numerical simulation, based on a single-carrier model, which takes into account carrier velocity modulation, the diffusion effect and realistic doping profile, enables us to illustrate the basic transport mechanisms involved in the device, chiefly the dynamic behaviour of the emission zonewidth. The effects of doping profile and material parameters on the device performances are considered for a frequency of 40 GHz. A high doping concentration near the injection plane is required to limit the positive resistance, and computed results indicate an optimum-doping spike value. An optimum efficiency of 3% and oscillation powers exceeding 20 mW for a device area of 10−5 cm2 are obtained with structures specified in the text. However, series-loss resistances have to be reduced as far as possible to maintain oscillation. Output power falls to 8 mW for a minimal series resistance estimated at 0.5Ω