ABSTRACT
In this chapter, the authors 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. They 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. The gapless energy spectrum of electrons and holes in graphene layers, graphene bilayers, and non-Bernal stacked multiple graphene layers opens up prospects of creating terahertz (THz) lasers based on the graphene structures. The authors describe the device structures under consideration and principles of their operation. The pertinent equations of the model governing the balance of electrons, holes, and optical phonons (rate equations) are presented. These equations are reduced to an equation governing the electron-hole effective temperature. The authors explain that the obtained results instill confidence in the future of graphene-based injection THz lasers although their realization might require a thorough optimization.
