Toward the creation of terahertz graphene injection laser

TL;DR

This paper investigates the potential for terahertz graphene injection lasers by analyzing electron-hole dynamics, temperature effects, and dynamic conductivity in graphene p-i-n structures, highlighting conditions for negative conductivity and lasing.

Contribution

It provides a theoretical analysis of population inversion and dynamic conductivity in graphene p-i-n structures, identifying conditions for terahertz lasing at room and lower temperatures.

Findings

Negative dynamic conductivity can occur in the terahertz range.

Electron-hole plasma cooling enhances terahertz lasing prospects.

Heating of optical phonons can hinder terahertz lasing at room temperature.

Abstract

We study the effect of population inversion associated with the electron and hole injection in graphene p-i-n structures at the room and slightly lower temperatures. It is assumed that the recombination and energy relaxation of electrons and holes is associated primarily with the interband and intraband processes assisted by optical phonons. The dependences of the electron-hole and optical phonon effective temperatures on the applied voltage, the current-voltage characteristics, and the frequency-dependent dynamic conductivity are calculated. In particular, we demonstrate that at low and moderate voltages the injection can lead to a pronounced cooling of the electron-hole plasma in the device i-section to the temperatures below the lattice temperature. However at higher voltages, the voltage dependences can be ambiguous exhibiting the S-shape. It is shown that the frequency-dependent dynamic conductivity can be negative in the terahertz range of freqiencies at certain values of the applied voltage. The electron-hole plasma cooling substantially reinforces the effect of negative dynamic conductivity and promotes the realization of terahertz lasing. On the other hand, the heating of optical phonon system can also be crucial affecting the realization of negative dynamic conductivity and terahertz lasing at the room temperatures.