We predict that graphene is a unique system where disorder-assisted scattering (supercollisions) dominates electron-lattice cooling over a wide range of temperatures, up to room temperature. This is so because for momentum-conserving electron-phonon scattering the energy transfer per collision is severely constrained due to a small Fermi surface size. The characteristic ${T}^{3}$ temperature dependence and power-law cooling dynamics provide clear experimental signatures of this new cooling mechanism. The cooling rate can be changed by orders of magnitude by varying the amount of disorder providing means for a variety of new applications that rely on hot-carrier transport.

Disorder-assisted electron-phonon scattering and cooling pathways in graphene.

Experimental measurements of the photoresponse in doped multilayer black phosphorus phototransistors show that the photocurrent generation is dominated by thermoelectric and bolometric processes, not by the photovoltaic effect.

Origin of photoresponse in black phosphorus phototransistors

Disorder-Assisted Electron-Phonon Scattering and Cooling Pathways in Graphene

A detailed carrier dynamics model for quantum well lasers is presented. The model describes the transport of carriers using full continuity equations and the gain by rate equations for each well separately, and it also takes into account electron-hole interactions which modify the energy band structure. To this end, the model includes Poisson and Schrodinger equations. The model is solved in steady state where it yields nonuniform carrier distributions along the crystal growth axis. Dynamically, the model is solved in the time domain, yielding the evolution of carriers in time and space and highlighting a new effect, photon-assisted carrier transport. The model is also solved in the small-signal regime where the phase lag in gain between wells is determined. >

On carrier injection and gain dynamics in quantum well lasers

INTERSUBBAND RELAXATION IN GaAs/Al x Ga 1-x As QUANTUM WELL STRUCTURES

The properties of hot electrons in systems where electrons and phonons experience quantum confinement are reviewed. The modifications to the behaviour of electrons and phonons brought about by confinement are described, particularly with reference to the principal scattering mechanism. The latter include the interaction with longitudinal optical phonons and plasmons, along with carrier-carrier effects. Some conflict in the literature concerning Fuchs-Kliewer polaritons is discussed. Low-temperature interactions with acoustic phonons are described. A central topic is that of energy relaxation, and the experimental and theoretical data relating to this form a large part of the review. Energy relaxation mechanisms in the femtosecond to nanosecond regimes, including intersubband and well-capture processes, are eventually summarized. An equally large section deals with hot-electron transport; in which negative differential resistance and other instabilities associated with parallel transport are discussed before turning to ballistic transport and impact ionization.

https://iopscience.iop.org/article/10.1088/0034-4885/54/2/001/pdf

B K Ridley

Papers

Hot electrons in low-dimensional structures