The effects of magnesium doping on the modal loss in AlGaN-based deep UV lasers
M. Martens1, C. Kuhn1, T. Simoneit1, S. Hagedorn2, A. Knauer2, T. Wernicke1, M. Weyers2, and M. Kneissl1,2
Published in:
Appl. Phys. Lett., vol. 110, no. 08, pp. 081103 (2017).
Abstract:
Absorption losses in the Mg-doped layers significantly contribute to the modal losses in group-III-nitride-based lasers. In this paper, we investigate the influence of Mg-doping on the modal absorption of optically pumped UVC lasers grown on epitaxially laterally overgrown AlN/sapphire substrates with an averaged threading dislocation density of 1×109cm-2. By varying the setback of the Mg-doping (∼1×1020cm-3) within the upper Al0.70Ga0.30N waveguide layer, the overlap of the optical mode with the Mg-doped region increases. For all structures, internal losses were derived from gain spectra obtained by the variable stripe length method. The internal losses increase from 10 cm-1 for lasers without Mg-doping to 28 cm-1 for lasers with a fully Mg-doped upper waveguide layer. The overlap of the optical mode with the Mg-doped waveguide ΓMg clearly correlates with the modal losses. This allows to calculate the Mg-induced losses in current injection laser diodes by αMgmod = ΓMg× 50 cm-1.
1 Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, EW 6-1, 10623 Berlin, Germany
2 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany
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