Emerging Josephson Junction/Graphene Device Technologies towards THz Signal Generation

Abstract

A novel approach to merge superconducting Josephson Junction (JJ) devices with nanoscale Graphene devices in order to achieve high gain-bandwidth-product on the order of THz was addressed. JJs are ultra-fast devices that consist of two superconducting plates separated by a nanoscale layer of nonconducting material which exhibits quantum tunneling phenomenon. While JJ-based devices have existed since nearly 1962, interfacing them with standard electrical systems has been a challenge for several reasons, including operating temperature, switching speed, and low-signal sensitivity. In this study, we investigated the possibility of utilizing JJ's so-called AC-effect in order to generate high frequency signals that can be accommodated by high speed nanoscale devices. Graphene Nano Ribbon Field Effect Transistors (GNRFET) have been emphasized for their very high frequency operation that is appropriate to accommodate the very high switching speed of the JJ devices. The study is based on the AC JJ effet with generating a sinusoidal current whose frequency directly scales with voltage. For a single-stage GNRFET CS amplifier, a gain of 35.7dB with a bandwidth of 217GHz was achieved, while 10.8dB with a unitary gain of 2.5THz was also accomplished. The paper details the design and interfacing of the JJ with GNRFET devices, targeting high frequency signal generation on the order of hundreds of GHz to THz.