Fabrication of reproducible air-bridged Schottky diodes for use at frequencies near 200 GHz

We report on the UK-based fabrication, optimisation and reproducibility of air-bridged, low capacitance, GaAs based Schottky diodes. A low value of on- wafer diode-to-diode variation of the DC parameters is crucial to the optimisation of these devices; the results reported include diodes with 2 mum diameter anodes exhibiting a 100 device average series resistance of 10.68 Omega (Standard deviation of 0.42 Omega), and diode ideality of 1.172 (0.005). Equivalent values of series resistance and ideality of 14.70 (0.81) Omega and 1.180 (0.004) respectively have been measured for 1 mum diameter anode devices. The low value of the standard deviations indicates good control of the diode fabrication process. Schottky diodes with 2 mum diameter anodes have been tested at 183 GHz in a sub-harmonic mixer where a double side band mixer noise temperature of 600 K and a conversion loss of 4.7 dB have been demonstrated.