Electron ensemble coherence and terahertz radiation amplification in a cascade superlattice structure

We report on an ensemble Monte Carlo study of the electron dynamics in a biased GaAs/AlGaAs cascade superlattice structure with domains of a strong electric field. We simulate the electron transport in a single superlattice, serving as an active region of the structure, and verify Kroemer's criterion which specifies over which distance in a superlattice a stable domain forms. We show that at room temperature in a superlattice with electrons subject to scattering at optical and acoustic phonons, the deviation of the superlattice length critical for domain development from that which is determined by Esaki–Tsu formula, varies from 10% to 300%. In a superlattice with the length larger than the critical one due to the electric field non-homogeneity, an electron ensemble becomes incoherent and its interaction with a terahertz field causes only the damping of the latter.