M. Schilling¹, N. Susilo¹, A. Muhin¹, G. Cardinali¹, J. Ruschel², H.K. Cho², J. Rass², J. Höpfner¹, T. Wernicke¹, S. Einfeldt², and M. Kneissl^1,2

Published in:

phys. stat. sol. (a), vol. 221, no. 23, pp. 2400392, doi:10.1002/pssa.202400392 (2024).

Abstract:

The effect of the active region growth temperature (T_MQW) on the external quantum efficiency (EQE) of AlGaN-based far-ultraviolet-C light-emitting diodes (far-UVC LEDs) emitting near 235 nm is investigated. AlGaN multi-quantum well (MQW) active regions are grown at temperatures between 850 and 1100 °C by metal-organic vapor-phase epitaxy, while special care is taken to keep aluminum mole fractions and thicknesses constant for all MQWs. Temperature- and excitation-power-dependent photoluminescence spectroscopy reveal a more than tenfold increase of the radiative recombination efficiency (RRE) when the growth temperature increases from 850 to 1020–1060 °C. The output powers for mounted far-UVC LEDs at 0.2 A increase from 0.5 mW for T_MQW of 900 °C to 2.5 mW for T_MQW of 1020 °C, corresponding to an increase in EQE from 0.04% to 0.23% at 0.2 A. However, lifetime measurements reveal a reduction of the L70 lifetime from 400 to 1 h when T_MQW increases from 900 to 1060 °C. In this investigation, it is shown that optimizing the growth conditions provides a promising approach to further increase the RRE and EQE and lifetime of far-UVC LEDs.

Topics:

AlGaN, external quantum efficiency, light-emitting-diodes, metal-organic vapor-phase epitaxy

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