M. Schilling¹, J. Ruschel², H.K. Cho², J. Rass², J. Höpfner¹, T. Wernicke¹, S. Einfeldt² and M. Kneissl^1,2

Published in:

Semicond. Sci. Technol., vol. 40, no. 4, pp. 045004, doi:10.1088/1361-6641/adbf40 (2025).

Abstract:

The effect of the quantum well (QW) number (n_QW) in far ultraviolet-C light emitting diodes (LEDs) on the optical power, external quantum efficiency (EQE) and degradation has been investigated. AlGaN-based multi-QW (MQW) LEDs designed for emission at 233 nm and 226 nm with n_QW between 1 and 30 are compared. A positive correlation between the optical power at 200 mA and L70 lifetime for large n_QW was observed. For the 233 nm LEDs QW numbers 6 ≤ n_QW ≤ 15 result in optical powers of 4–5 mW at 200 mA (corresponding to a maximum EQE of 0.47% for n_QW = 15) and L70 lifetimes of 9–13 h. For n_QW = 30 a reduction of output power and L70 lifetime was found indicating an optimum n_QW for 233 nm LEDs. For the 226 nm LEDs a constant optical power of 0.5 mW at 200 mA (corresponding to an EQE of 0.05%) was measured independent of n_QW. However, the L70 lifetime continuously increases from 7 h for 3 QWs to 13 h for 18 QWs. The enhanced optical power accompanied by a reduced degradation is attributed to a reduced hole leakage from the MQW into the n-side and reduced local charge carrier density per QW for large n_QW.

Keywords:

AlGaN, far-UVC LEDs, multi-quantum well, MOVPE, external quantum efficiency

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