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Carrier distribution, spontaneous emission, and gain in self-assembled quantum dot lasers

Gmachl, Claire F., Smowton, Peter Michael ORCID:, Pearce, Emma J., Lutti, Julie, Matthews, Daniel R., Summers, Huw D., Lewis, Gareth M., Blood, Peter, Hopkinson, Mark, Krysa, Andrey and Bour, David P. 2004. Carrier distribution, spontaneous emission, and gain in self-assembled quantum dot lasers. Presented at: Integrated Optoelectronic Devices 2004, San Jose, California, USA, Published in: Gmachl, C. F. and Bour, D. P. eds. Novel In-Plane Semiconductor Lasers III, Proceedings of the Conference held at San Jose, CA, 26 January 2004. SPIE Proceedings , vol.5365 Bellingham, WA: SPIE, p. 86. 10.1117/12.530429

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We examine the mechanisms that lead to a low value of saturated modal gain in both 1μm emitting InGaAs based and ≈ 700nm emitting InP/GaInP quantum dot laser systems. We explain the observation that the value of the saturated modal gain increases as the temperature decreases using a simple model of the filling of the available dot and wetting layer states according to a Fermi-Dirac distribution. We show that it is the relatively large number of available wetting layer valence states and their proximity in energy to the dot states that limits the modal gain. We measure the population inversion factor for samples containing different numbers of layers of dots and for samples where the dots are grown in a quantum well (DWELL) and for dots grown in bulk layers of either GaAs or Al0.15Ga0.85As (non-DWELL). Comparison of this data with that calculated for a Fermi-Dirac distribution of carriers in the available states demonstrates that for most of the samples the carriers in the ground states of the quantum dots are not in thermal equilibrium with those in higher lying energy states - the excited states or wetting layer.

Item Type: Conference or Workshop Item (Paper)
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QC Physics
Publisher: SPIE
ISBN: 9780819452733
ISSN: 0277786X
Last Modified: 25 Oct 2022 09:40

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