Theory of nonequilibrium quantum transport and energy dissipation in terahertz quantum cascade lasers

T. Kubis, C. Yeh, P. Vogl, A. Benz, G. Fasching, and C. Deutsch
Phys. Rev. B 79, 195323 – Published 22 May 2009

Abstract

We analyze theoretically several crucial performance aspects of terahertz quantum cascade lasers, such as the impact of doping on the threshold current, the relative importance of the various scattering mechanisms, and the balance of coherent transport and realistic energy dissipation. We have developed a fully self-consistent model for stationary charge transport based on nonequilibrium Green’s function theory that takes into account incoherent scattering with phonons, impurities, and rough interfaces as well as electron-electron scattering in the Hartree approximation, but does not a priori assume the electron distributions to follow the periodicity of the quantum cascade laser (QCL) structure. The theoretical results show excellent quantitative agreement with experimental data. We find scattering at rough interfaces to strongly affect electronic transport and efficiently limit the optical gain. Our results also indicate that a large portion of the current is maintained by coherent multibarrier tunneling. We show that this dominant coherent transport may lead to electron distributions that do not follow the periodicity of the QCL.

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  • Received 23 April 2009

DOI:https://doi.org/10.1103/PhysRevB.79.195323

©2009 American Physical Society

Authors & Affiliations

T. Kubis*, C. Yeh, and P. Vogl

  • Walter Schottky Institute, Technische Universität München, Am Coulombwall 3, 85748 Garching, Germany

A. Benz, G. Fasching, and C. Deutsch

  • Photonics Institute and Center for Micro- and Nanostructures, Vienna University of Technology, Gusshausstrasse 29/387, A-1040 Vienna, Austria

  • *tillmann.kubis@wsi.tum.de

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Vol. 79, Iss. 19 — 15 May 2009

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