Abstract
We use a split top gate to induce doping of opposite signs in different parts of a graphene field-effect transistor, thereby effectively forming a graphene thermocouple. The thermocouple is sensitive to the electronic temperature in graphene, which can be several hundred kelvin higher than the ambient one at sufficiently high bias current. Combined with the high thermoelectric power of graphene, this allows for i) simple measurements of the electronic temperature and ii) building thermoelectric radiation detectors. A simple prototype graphene thermoelectric detector shows a temperature-independent optical responsivity of around 400 V/W at 94 GHz at temperatures of 4–50 K.
Highlights
In graphene, the Seebeck coefficient S (or thermopower (TEP)) is large, reaching values around 100 μV/K ~ kB/e1–3
The electron–phonon coupling in graphene is weak, which can result in significantly different effective temperatures of the electronic and bosonic subsystems when the former is pushed out of equilibrium by a current flowing through the graphene[10]
The electronic temperature Te can be assessed by measuring the shot noise, for example
Summary
The Seebeck coefficient S (or thermopower (TEP)) is large, reaching values around 100 μV/K ~ kB/e1–3 This raises the possibility of a new type of radiation detector based on this effect. This measurement technique is based on first principles and is straightforward Several such experiments have shown unambiguously that the electronic temperature can reach several hundred degrees at a high bias current[10], which was identified as a working mechanism for the intrinsic photo response in graphene[6]. The small volume of graphene would allow for extremely fast bolometric devices, very likely outperforming the state-of-the-art hot-electron bolometers This technique does not seem to be particular suitable for measuring small changes in the electronic temperature. The noise equivalent power is 20–30 pW/Hz0.5 when using an ordinary lock-in measurement system
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