High-mobility boron-nitride encapsulated graphene is a well-known model system for quantum electronics, spintronics, plasmonics, optolectronics, and strongly interacting electron physics. It is also a platform for out-of-equilibrium physics thanks to its electric-field strength and large current carrying capability. I will illustrate some high-field graphene properties in the geometry of the so-called Zener-Klein-tunneling transistor.
I will first introduce the Zener-Klein tunneling field effect transistor (ZKT-FET) istelf [1], its different transport regimes in increasing electric field: diffusive, velocity saturation, Zener-Klein tunneling, and finally the drain-voltage induced bipolar regime where the graphene transistor behaves as a light emitting diode (ZKT-LED).
Different regimes have signatures in the energy relaxation mechanisms which are monitored by microwave noise thermometry. In particular, ZKT-FETs benefit from electroluminescent cooling by the hyperbolic phonon polariton (HPhP) modes of the hBN substrate [2]. This near-field radiative cooling is quite unique and efficient; it can be directly detected as a mid-infrared light in the far-field. Conversely, HPhP emission plays an important role in the mid-infrared response ZKT-FETs [3].
If time permits, I will discuss two more phenomena observed in ZKT-FETs. The first is the breakdown of quantum Hall effect (QHE), which is mediated by a collective magneto-exciton instability [4]. The second revisits the old problem of flicker noise at the light of the tunability of relation mechanisms in ZKT-FETs.
[1] W. Yang et al., Nat. Nanotech. 13, 47 (2018)
[2] E. Baudin et al., Adv. Funct. Mater., 1904783 (2019)
[3] P. Huang et al., Nature Comm. 11, 863 (2020)
[4] W. Yang et al., Phys. Rev. Lett. 121, 136804 (2018)