Probing scattering mechanisms with symmetric quantum cascade lasers

Christoph Deutsch, Vienna University of Technology
Hermann Detz, Vienna University of Technology
Tobias Zederbauer, Vienna University of Technology
Aaron M. Andrews, Vienna University of Technology
Pavel Klang, Vienna University of Technology
Tillmann Kubis, Birck Nanotechnology Center, Purdue University
Gerhard Klimeck, Network for Computational Nanotechnology, Birck Nanotechnology Center, Purdue University
Manfred E. Schuster, Max Planck Society
Werner Schrenk, Vienna University of Technology
Gottfried Strasser, Vienna University of Technology
Karl Unterrainer, Vienna University of Technology

Abstract

A characteristic feature of quantum cascade lasers is their unipolar carrier transport. We exploit this feature and realize nominally symmetric active regions for terahertz quantum cascade lasers, which should yield equal performance with either bias polarity. However, symmetric devices exhibit a strongly bias polarity dependent performance due to growth direction asymmetries, making them an ideal tool to study the related scattering mechanisms. In the case of an InGaAs/GaAsSb heterostructure, the pronounced interface asymmetry leads to a significantly better performance with negative bias polarity and can even lead to unidirectionally working devices, although the nominal band structure is symmetric. The results are a direct experimental proof that interface roughness scattering has a major impact on transport/lasing performance. (C) 2013 Optical Society of America

Discipline(s)

Nanoscience and Nanotechnology