Graphene and Lateral Heterostructure for THz Imaging

Abstract

We report millimeter-wave and sub-terahertz detection using graphene FETs up to 220 GHz at zero-bias to reduce $1/f $ noise. Detection leveraged the nonlinearity of the channel resistance through resistive field-effect transistor mixing for high-dynamic range. At a 50- $\Omega$ load, measured detection responsivity was 70 V/W at 2 GHz to 33 V/W at 110 GHz. The measured noise power of the graphene FETs was ${\sim}{\hbox{7.5}} \times {\hbox{10}}^{-18}$ V $^{2}$ /Hz at zero-bias. Noise equivalent power at 110 GHz was estimated to be $\sim {\hbox{80}}$ pW/Hz $^{0.5}$ . A linear dynamic range of ${>} {\hbox{40}}$ dB was measured, providing 15–20 dB greater linear dynamic range compared to conventional CMOS detectors at the transistor level. The emerging graphene heterostructure diodes offer the RC limited cutoff frequency $(f_{\rm c})$ of 2.9 THz with the noise equivalent power of ${\sim} {\hbox{8}}$ pW/Hz $^{0.5}$ at 200 GHz due to its small junction- capacitance and diode nonlinearity.