A monolithic 60 GHz diode mixer in FET compatible technology

A method of simultaneously fabricating MESFETs with a maximum frequency of oscillation (f/sub max/) of 70 GHz and Schottky diodes with a gain-bandwidth product (f/sub T/) of approximately=2300 GHz to produce a 60-GHz mixer is given. A deep selective n/sup +/ implantation for a buried n/sup +/ zone under the mixer diode was used. Metalorganic chemical vapor deposition (MOCVD) was used for the growth of the active n layer and an n/sup +/ surface contact layer. The MESFETs and the diodes were both fabricated with a recessed Schottky contact structure using Ti-Pt-Au metallization. Arrays of 30 different diodes and 55 different MESFETs were fabricated to study the process technology and to get optimum devices for a receiver chip containing a diode balanced mixer plus a low-noise intermediate-frequency (IF) amplifier. The conversion loss and noise figures of the diodes were measured and compared with those obtained from computer simulations. Both large- and small-signal analysis are included. The 60-GHz balanced mixer chip shows a conversion loss of 6.0 dB and a double-sideband noise figure of 3.3 dB.<>