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Proceedings Paper

Characterisation of modulation doped quantum dot lasers
Author(s): Peter M. Smowton; Ian C. Sandall; Craig L. Walker; John D. Thomson; Angela Sobiesierski; Tom Badcock; David J. Mowbray; Hui-Yun Liu; Mark Hopkinson
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Paper Abstract

Self-assembled In(Ga)As quantum dot (QD) lasers incorporating p-type modulation doping have generated much interest recently due to reports of a temperature insensitive threshold current and increased modulation bandwidth. The mechanism by which p-type doping improves the performance of QD lasers is thought to be similar to that envisaged for quantum well lasers, where increased gain is expected for a given quasi-Fermi level separation due to a shift in both quasi-Fermi levels towards the valence states. However, the benefits may be much more pronounced in quantum dot structures since the population of the smaller number of dot states can be dramatically affected using relatively low doping levels, which may incur less penalty with regard to increased non-radiative recombination and internal optical mode loss. We present results of direct measurements of the modal gain measured as a function of the quasi-Fermi level separation for samples with different degrees of doping, which demonstrate unambiguously the increased gain that can be obtained at a fixed quasi-Fermi level separation. In addition, we have measured the internal optical mode loss and radiative and non-radiative recombination currents for samples containing 0, 15 and 50 dopant atoms per dot and show that, although the internal optical mode loss is similar for all three samples, the non-radiative recombination current increases for samples containing p-doping. We show that our experimental results are consistent with a simple computer simulation of the operation of our structures.

Paper Details

Date Published: 22 February 2006
PDF: 13 pages
Proc. SPIE 6133, Novel In-Plane Semiconductor Lasers V, 61330T (22 February 2006); doi: 10.1117/12.650682
Show Author Affiliations
Peter M. Smowton, Cardiff Univ. (United Kingdom)
Ian C. Sandall, Cardiff Univ. (United Kingdom)
Craig L. Walker, Cardiff Univ. (United Kingdom)
John D. Thomson, Cardiff Univ. (United Kingdom)
Angela Sobiesierski, Cardiff Univ. (United Kingdom)
Tom Badcock, The Univ. of Sheffield (United Kingdom)
David J. Mowbray, The Univ. of Sheffield (United Kingdom)
Hui-Yun Liu, The Univ. of Sheffield (United Kingdom)
Mark Hopkinson, The Univ. of Sheffield (United Kingdom)

Published in SPIE Proceedings Vol. 6133:
Novel In-Plane Semiconductor Lasers V
Carmen Mermelstein; David P. Bour, Editor(s)

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