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
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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