Broadband Flexible Graphene RF Power Detectors

Abstract

With the development of wearable radios, foldable Wi-Fi devices, and conformal wireless sensors,flexible radio frequency (RF) electronics have become a highly active research field [1, 2]. As anessential component for both RF transmitters and receivers, a power detector is required to withstandhigh levels of strain. The flexible RF power detectors based on laminated Si and III-V membranes onpolymer substrates demonstrate poor mechanical reliability, restricting the range of applications [3, 4].In contrast, graphene is an ideal candidate for the use in flexible RF power detectors, because it offersoutstanding electrical and mechanical properties [5]. Furthermore, graphene can be grown over largeareas by chemical vapour deposition and transferable to various flexible substrates [6].In this work, we demonstrate RF power detection up to 67 GHz using coplanar access graphene field -effect transistors (GFETs) on flexible and transparent polyethylene terephthalate substrates. Thefrequency dependence of measured and modelled voltage responsivity at optimum gate bias is shownin Figure 1. At room temperature, this detector reveals voltage responsivity above 10 V/W over thefrequency range from 1 GHz to 67 GHz. The measured voltage responsivity results are well fitted by thenonlinear empirical model [7] with all parameters extracted from S-parameter and DC measurements.In addition, we study the effects of interfacial capacitance, associated with traps, on the hysteresis ofvoltage responsivity. Figure 2 shows the measured voltage responsivity as a function of the gate voltagewith reproducible hysteresis loop at 55 GHz