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Low-threshold AlGaN-based UVB VCSELs enabled by post-growth cavity detuning

G. Cardinali1, F. Hjort2, N. Prokop1, J. Enslin1, M. Cobet1, M.A. Bergmann2, J. Gustavsson2, J. Ciers2, I. Häusler3, T. Kolbe4, T. Wernicke1, Å. Haglund2, and M. Kneissl1,4

Published in:

Appl. Phys. Lett., vol. 121, no. 10, pp. 03501, doi:10.1063/5.0097903 (2022).


The performance of vertical-cavity surface-emitting lasers (VCSELs) is strongly dependent on the spectral detuning between the gain peak and the resonance wavelength. Here, we use angle-resolved photoluminescence spectroscopy to investigate the emission properties of AlGaN-based VCSELs emitting in the ultraviolet-B spectral range with different detuning between the photoluminescence peak of the quantum-wells and the resonance wavelength. Accurate setting of the cavity length, and thereby the resonance wavelength, is accomplished by using doping-selective electrochemical etching of AlGaN sacrificial layers for substrate removal combined with deposition of dielectric spacer layers. By matching the resonance wavelength to the quantum-wells photoluminescence peak, a threshold power density of 0.4 MW/cm2 was achieved, and this was possible only for smooth etched surfaces with a root mean square roughness below 2 nm. These results demonstrate the importance of accurate cavity length control and surface smoothness to achieve low-threshold AlGaN-based ultraviolet VCSELs.

1 Institute of Solid State Physics, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
2 Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Gothenburg, Sweden
3 Institute of Optics and Atomic Physics, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
4 Ferdinand-Braun-Institut (FBH), Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany


Photoluminescence spectroscopy, Emission spectroscopy, Semiconductors, Optical resonators, Optical field, Etching, Epitaxy, Quantum wells, Lasers

© 2022 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). https://doi.org/10.1063/5.0097903

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