AlGaN/GaN Distributed Schottky Barrier Single-Pole Single-Throw Millimeter-Wave Switches

This paper presents two designs of millimeter-wave single-pole single-throw switches based on AlGaN/GaN heterostructure. The switches are based on two approaches to the travelling wave concept with Schottky barrier shunt elements integrated into a coplanar waveguide. The first design utilizes a two-stage artificial transmission line topology with distributed shunt elements in Schottky diode configuration. The second one employs a single electrically large shunt element configured as a high electron mobility transistor. Both arrangements allow the switches to achieve very high operational bandwidth, exceeding 100 GHz, without the requirement for very high lithography resolution. Examined switches were fabricated in a 2-mu m GaN-on-SiC process. Measurement results demonstrate upper operating frequencies exceeding 114.5 GHz starting from 14 GHz or even DC, depending on the design. The W band on-off ratio over 17 dB and 21 dB is achieved by the first and second construction, respectively. Measurements of transient parameters show that high switching speed can also be achieved (rise/fall time as low as <= 17 ns for the first construction).