Ultraviolet‑B Resonant-Cavity Light-Emitting Diodes with Tunnel Junctions and Dielectric Mirrors
E. Torres1, J. Ciers1, M.A. Bergmann1, J. Höpfner2, S. Graupeter2, M. Grigoletto2, M. Guttmann3, T. Kolbe3, T. Wernicke2, M. Kneissl2,3, and Å. Haglund1
Published in:
ACS Photonics, vol. 11, no. 8, pp. 2923-2929, doi:10.1021/acsphotonics.4c00312 (2024).
Abstract:
We demonstrate the first electrically injected AlGaN-based ultraviolet-B resonant-cavity light-emitting diode (RCLED). The devices feature dielectric SiO2/HfO2 distributed Bragg reflectors enabled by tunnel junctions (TJs) for lateral current spreading. A highly doped n++-AlGaN/n++-GaN/p++-AlGaN TJ and a top n-AlGaN current spreading layer are used as transparent contacts, resulting in a good current spreading up to an active region mesa diameter of 120 µm. To access the N-face side of the device, the substrate is removed by electrochemically etching a sacrificial n-AlGaN layer, leading to a smooth underetched surface without evident parasitic etching in the n- and n++-doped layers of the device. The RCLEDs show a narrow emission spectrum with a full width at half-maximum (FWHM) of 4.3 nm compared to 9.4 nm for an ordinary LED and a more directional emission pattern with an angular FWHM of 52° for the resonance at 310 nm in comparison to ∼126° for an LED. Additionally, the RCLEDs show a much more stable emission spectrum with temperature with a red-shift of the electroluminescence peak of about ∼18 pm/K and a negligible change of the FWHM compared to LEDs, which shift ∼30 pm/K and show spectrum broadening with temperature. The demonstration of those devices, where a highly reflective mirror is spatially separated from an ohmic metal contact, opens up a new design space to potentially increase the poor light extraction efficiency in UV LEDs and is an important step toward electrically injected UV vertical-cavity surface-emitting lasers.
1 Department of Microtechnology and Nanosciense, Chalmers University of Technology, 41296 Gothenburg, Sweden
2 Institute of Solid State Physics, Technische Universität Berlin, 10623 Berlin, Germany
3 Ferdinand-Braun-Institut (FBH), 12489 Berlin, Germany
Keywords:
ultraviolet, AlGaN, resonant-cavity light-emitting diode, electrochemical etching, tunnel junction
© 2024 The Authors. Published by American Chemical Society
This article is licensed under CC-BY 4.0.
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