Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 9: Semiconductor Laser II

HL 9.6: Talk

Monday, March 26, 2007, 16:00–16:15, H13

Low threshold high efficiency InAs/InGaAlAs/InP ∼1.55 µm quantum dash-in-a-well lasers — •Sebastian Hein, André Somers, Sven Höfling, and Alfred Forchel — Technische Physik, Physikalisches Institut, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany

In this work the dash-in-a-well (DWELL) design was used to improve the basic characteristics of InP-based quantum dash lasers. By embedding self-assembled InAs QDashes in a quantum well threshold current densities could be reduced due to an enhanced carrier capture of the QDashes. However the well layers reduce the energy barrier and hence lower the energy levels of the QDashes resulting in a longer emission wavelength. Though the QDash emission wavelength can be tuned over a wide range by varying the thickness of the QDash layers, the critical layer thickness for the formation of QDashes poses a lower limit to adjustment. Employing an adapted InAs/In_0.53Ga_0.37Al_0.10As/In_0.53Ga_0.23Al_0.24As DWELL design, threshold current densities could be significantly reduced while maintaining an emission wavelength near 1.55 µm. Cavity length dependent measurements of as-grown devices lead to an extrapolated transparency current density of 165 A/cm² per dash layer and a very high internal differential efficiency of 0.89. With 0.6 mm long devices a very high external differential efficiency of 0.20 W/A per facet was achieved.