Journal Articles

We have fabricated epitaxial side-gate graphene field-effect transistors (FETs) with high transconductance. A side-gate graphene FET with 5560 nm2 active channel dimensions and a lateral gate-channel separation of 95 nm showing a high transconductance of 590 mS/mm is presented. An estimation of the electrostatic gate-channel capacitance of epitaxial side-gate graphene FETs shows that it is in the same order as the electrostatic gate capacitance of common top-gate graphene MOSFETs justifying the high transconductances of our devices. The results of the present paper demonstrate the potential of the side-gate architecture for graphene transistors.

Superconducting radiation sensors are of particular interest for imaging applications in the sub-mm wavelength band because of their extraordinary sensitivity. The rising number of sensors integrated in one array entails the requirement of multiplexing techniques in order to reduce the number of wires leading into the cryogenic stage and thus reduce the thermal losses. One kind of promising code division multiplexing technique is based on a current steering switch (CSS), which is composed of two identical superconducting quantum interference devices (SQUIDs) in parallel current paths. One of them is switched from the superconducting into the normal state controlled by the applied magnetic flux. In this way the signal path can be altered and they can act as a polarity switch for analogue signals. We pursue this concept to use rapid single flux quantum (RSFQ) electronics for controlling these switches. As a first step, the SQUIDs of the CSS are inductively coupled to the storing loops of two delay flip flops (DFFs). Thus, one is able to toggle the polarity of the analogue switch by controlling the state of the DFF by RSFQ control signals. The results of simulations and measurements and also margin analyses are discussed.