title: Probing scattering mechanisms with symmetric quantum cascade lasers.
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.
authors.affiliation: Photonics Institute and Center for Micro- and Nanostructures, Vienna University of Technology, Gusshausstrasse 27–29, 1040 Vienna, Austria. christoph.deutsch@tuwien.ac.at
authors.forename: Christoph
authors.initials: C
authors.lastname: Deutsch
authors.forename: Hermann
authors.initials: H
authors.lastname: Detz
authors.forename: Tobias
authors.initials: T
authors.lastname: Zederbauer
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Andrews
authors.forename: Pavel
authors.initials: P
authors.lastname: Klang
authors.forename: Tillmann
authors.initials: T
authors.lastname: Kubis
authors.forename: Gerhard
authors.initials: G
authors.lastname: Klimeck
authors.forename: Manfred E
authors.initials: ME
authors.lastname: Schuster
authors.forename: Werner
authors.initials: W
authors.lastname: Schrenk
authors.forename: Gottfried
authors.initials: G
authors.lastname: Strasser
authors.forename: Karl
authors.initials: K
authors.lastname: Unterrainer
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D007834:Lasers; D008027:Light; D011789:Quantum Theory; D012031:Refractometry / Q000295:instrumentation* / Q000379:methods*; D012542:Scattering, Radiation