Transport in photoactive graphene heterostructures, originating from the dynamics of photogenerated hot carriers, is governed by the processes of thermionic emission, electron-lattice thermal imbalance and cooling. These processes give rise to interesting photoresponse effects, in particular negative differential resistance (NDR) arising in the hot-carrier regime. The NDR effect stems from a strong dependence of electron-lattice cooling on the carrier density, which results in the carrier temperature dropping precipitously upon increasing bias. The ON-OFF switching between the NDR regime and the conventional cold emission regime, as well as the gate-controlled closed-circuit current that is present at zero bias voltage, can serve as signatures of hot-carrier dominated transport.
@article{arxiv.1501.06927,
title = {Thermionic Emission and Negative dI/dV in Photoactive Graphene Heterostructures},
author = {J. F. Rodriguez-Nieva and M. S. Dresselhaus and L. S. Levitov},
journal= {arXiv preprint arXiv:1501.06927},
year = {2015}
}