Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 85: Poster Session II

HL 85.56: Poster

Thursday, March 17, 2011, 18:00–21:00, P4

1550 nm quantum dot lasers with high modal gain — Christian Gilfert, •Vitalii Ivanov, and Johann Peter Reithmaier — Technische Physik, Institute of Nanostructure Technologies and Analytics, University of Kassel, Heinrich-Plett Str. 40, D-34132 Kassel, Germany

In the last years a strong effort was made in the development of InP based quantum dot (QD) structures to obtain high performance 1550 nm lasers. However, most of the work is related to QDash active materials. In this work the conditions for the formation of InAs QDs and QDashes on the quaternary InAlGaAs surfaces, lattice-matched to n-type InP (100) were investigated. It could be shown that the supply of different types of As molecules allow to switch between QDs and QDashes growth modes. A formation of rather round-shaped dots was observed under As2 atmosphere. These new type of QD layers exhibited a significantly reduced height distribution, which reduces the inhomogeneous linewidth to about 23 meV (see APL 96, 191903 (2010)). Based on these QD structures diode lasers with an SCH design were realized. The laser structure consists of 6 QD layers embedded in an InGaAlAs core waveguide and 1700 nm InP top cladding layer. The QD lasers exhibit a low internal absorption of 8 cm-1 and a rather high modal gain of about 60 cm-1, which is nearly a factor of two higher than for any other reported comparable InP based QD laser. We attribute this strong improvement to a much higher spectral gain, which is consistent with the observed very narrow photoluminescence linewidth.