Modeling bound-to-continuum terahertz quantum cascade lasers: The role of Coulomb interactions

TL;DR

This paper demonstrates the critical importance of accurately modeling Coulomb interactions, including space charge effects and scattering, in predicting the behavior of bound-to-continuum terahertz quantum cascade lasers.

Contribution

It introduces a comprehensive modeling approach that incorporates full Coulomb screening, spin dependence, and iterative Schrödinger-Poisson simulations for these lasers.

Findings

Simplified Coulomb models lead to significant deviations.

Full Coulomb screening and spin effects are essential for accuracy.

Iterative Schrödinger-Poisson simulations are necessary for space charge effects.

Abstract

Based on an ensemble Monte Carlo analysis, we show that Coulomb interactions play a dominant role in bound-to-continuum terahertz quantum cascade lasers and thus require careful modeling. Coulomb interactions enter our simulation in the form of space charge effects as well as Coulomb scattering events. By comparison to a full many-subband Coulomb screening model, we show that simplified approaches produce considerable deviations for such structures. Also the spin dependence of electron-electron scattering has to be adequately considered. Moreover, we demonstrate that iterative Schr\"{o}dinger-Poisson and carrier transport simulations are necessary to correctly account for space charge effects.