Integrated silicon Schottky mixer diodes with cutoff frequencies above 1 THz

In this paper, fully monolithic integrated Schottky diodes on a high-resistivity (HR) silicon substrate with cutoff frequencies above 1 THz are presented. As HR silicon substrate, a common float-zone substrate was used. The necessity of an optimized layer design will be discussed. As it will be shown, cutoff frequencies above 1 THz are possible even for large area diodes with an optimized layer design, which provides the so-called MOTT operation. The demands for the layer design to realize MOTT operation and the resulting advantages for the component will be discussed in detail. The used fabrication process, which combines two separate standard processes, is explained briefly. The results of the electrical measurements and the achieved cutoff frequency will be summarized. To demonstrate a monolithic integration, the presented Schottky diodes have been manufactured in a process wherein RF microelectromechanical systems switches have been successfully produced. As a key application, a subharmonic mixer, with a 24-GHz RF signal and a 12-GHz local-oscillator signal, will be discussed.