  Optical excitation and subsequent decay of graphene plasmons can produce a
significant increase in charge-carrier temperature. An efficient method to
convert this temperature elevation into a measurable electrical signal at room
temperature can enable important mid-infrared applications such as thermal
sensing and imaging in ubiquitous mobile devices. However, as appealing as this
goal might be, it is still unrealized due to the modest thermoelectric
coefficient and weak temperature-dependence of carrier transport in graphene.
Here, we demonstrate mid-infrared graphene detectors consisting of arrays of
plasmonic resonators interconnected by quasi one-dimensional nanoribbons.
Localized barriers associated with disorder in the nanoribbons produce a
dramatic temperature dependence of carrier transport, thus enabling the
electrical detection of plasmon decay in the nearby graphene resonators. We
further realize a device with a subwavelength footprint of 5*5 um2 operating at
12.2 um, an external responsivity of 16 mA/W, a low noise-equivalent power of
1.3 nW/Hz1/2 at room temperature, and an operational frequency potentially
beyond gigahertz. Importantly, our device is fabricated using large-scale
graphene and possesses a simple two-terminal geometry, representing an
essential step toward the realization of on-chip graphene mid-infrared detector
arrays.
