Recombination mechanisms and thermal droop in AlGaN-based UV-B LEDs

C. De Santi1, M. Meneghini1, D. Monti1, J. Glaab2, M. Guttmann3, J. Rass2, S. Einfeldt2, F. Mehnke3, J. Enslin3, T. Wernicke3, M. Kneissl2,3, G. Meneghesso1, and E. Zanoni1

Published in:

Photonics Res., vol. 5, no. 2, pp. A44-A51 (2017).

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Abstract:

This paper reports a comprehensive analysis of the origin of the electroluminescence (EL) peaks and of the thermal droop in UV-B AlGaN-based LEDs. By carrying out spectral measurements at several temperatures and currents, (i) we extract information on the physical origin of the various spectral bands, and (ii) we develop a novel closed-form model based on the Shockley-Read-Hall theory and on the ABC rate equation that is able to reproduce the experimental data on thermal droop caused by non-radiative recombination through deep levels. In the samples under test, the three EL bands are ascribed to the following processes: band-to-band recombination in the quantum wells (main EL peak), a parasitic intra-bandgap radiative transition in the quantum well barriers, and a second defect-related radiative process in the p-AlGaN superlattice.

1 Department of Information Engineering, University of Padova, via Gradenigo 6/B, Padova 35131, Italy
2 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany
3 Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, EW 6-1, 10623 Berlin, Germany

OCIS codes:

(230.3670) Light-emitting diodes; (230.0250) Optoelectronics; (250.5590) Quantum-well, -wire and -dot devices.