Depletion of carriers and negative differential conductivity in an intrinsic graphene under a dc electric field

TL;DR

This paper investigates carrier heating, depletion, and negative differential conductivity in intrinsic graphene under a dc electric field, considering phonon interactions and recombination processes, revealing temperature-dependent electrical behaviors.

Contribution

It provides a detailed analysis of the transient and steady-state electrical responses of graphene, including the effects of phonon-induced recombination and energy relaxation, which were not comprehensively studied before.

Findings

Nearly-linear I-V characteristic up to 20 kV/cm at room temperature

Carrier depletion occurs below 250 K due to optical phonon recombination

Negative differential conductivity appears below 170 K at low fields

Abstract

The heating of carriers in an intrinsic graphene under an abrupt switching off a dc electric field is examined taking into account both the energy relaxation via acoustic and optic phonons and the interband generation-recombination processes. The later are caused by the interband transitions due to optical phonon modes and thermal radiation. Description of the temporal and steady-state responses, including the nonequilibrium concentration and energy as well as the current-voltage characteristics, is performed. At room temperature, a nearly-linear current-voltage characteristic and a slowly-varied concentration take place for fields up to -- 20 kV/cm. Since a predominant recombination of high-energy carriers due to optical phonon emission at low temperatures, a depletion of concentration takes place below -- 250 K. For lower temperatures the current tends to be saturated and a negative differential conductivity appears below -- 170 K in the region of fields -- 10 V/cm.