Dresden 2006 – scientific programme

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HL: Halbleiterphysik

HL 2: Symposium THz-quantum cascade lasers

HL 2.5: Fachvortrag

Monday, March 27, 2006, 12:15–12:45, HSZ 01

GaInAs/AlAsSb quantum cascade lasers: a new approach towards 3-to-5 µm semiconductor lasers — •Joachim Wagner, Quankui Yang, Christian Manz, Wolfgang Bronner, Christian Mann, and Klaus Köhler — Fraunhofer-Institut für Angewandte Festkörperphysik (IAF), Tullastrasse 72, 79108 Freiburg, Germany

Quantum cascade (QC) lasers based on the GaInAs/AlInAs-on-InP materials combination yield high-performance devices in the 5-to-10 µm wavelength range. These lasers can be operated in cw mode up to room-temperature and in pulsed mode up to 400-500K. Towards shorter wavelengths GaInAs/AlInAs QC laser performance rolls off due to insufficient carrier confinement caused by the limited available conduction- band offset, which is in the 500-700 meV range. A more than twofold increase in con-duction band offset can be achieved when using lattice matched AlAsSb rather than AlInAs as barrier material. For the GaInAs/AlAsSb materials combination the offset for the direct conduction band minimum amounts to 1.6 eV. Compared to alternative con-cepts for large conduction band offset QC structures, such as the GaN/AlN or InAs/AlSb materials combinations, the present approach has the significant advantage to make use of the mature fabrication technology available for InP-based lasers.
In spite of the challenges in materials growth, GaInAs/AlAsSb and even quaternary barrier GaInAs/AlGaAsSb QC lasers emitting in the 4-4.5 µm range have been grown by molecular-beam epitaxy. In pulsed mode operation, GaInAs/AlAsSb QC lasers ex-hibit a peak output power of up to 900 mW room-temperature, while their maximum operating temperature lies above 400 K. Furthermore, GaInAs/AlAsSb DFB QC lasers have been demonstrated, showing single-mode emission at 4.08 µm for pulsed mode room-temperature operation.