AlGaN/AlN Stranski–Krastanov Quantum Dots for
Highly Efficient Electron Beam-Pumped Emitters: The Role of Miniaturization
and Composition to Attain Far UV‑C Emission
posted on 2023-11-07, 16:42authored byJesus Cañas, Anjali Harikumar, Stephen T. Purcell, Nevine Rochat, Adeline Grenier, Audrey Jannaud, Edith Bellet-Amalric, Fabrice Donatini, Eva Monroy
Conventional
ultraviolet lamps for disinfection emit radiation
in the 255–270 nm range, which poses a high risk of causing
cancer and cataracts. To address these concerns, solid-state UV-C
sources emitting below 240 nm are attractive as a safe and sustainable
disinfection solution for occupied spaces. This article delves into
the extension of AlxGa1–xN/AlN quantum dot (QD) technology toward the far
UV-C range. The structural and optical impact of increasing the Al
content in the QDs through the increase of the Al flux and eventual
correction of the Ga flux, and the effect of extreme miniaturization
of the QDs achieved by reducing their growth time, are explored. The
internal quantum efficiency of self-assembled QDs, grown with a metal/N
ratio ranging from 0.5 to 0.8, remains around 50% regardless of the
Al content (up to 65%) or emission wavelength (300–230 nm).
However, QDs emitting below 270 nm display bimodal luminescence due
to inhomogeneous in-plane emission caused by fluctuations in the QD
shape linked to extended defects. Reducing the QD size exacerbates
this bimodality without altering the emission wavelength. Power efficiencies
under electron beam pumping range from 0.4 to 1%, with the potential
for improvement through surface treatments enhancing light extraction
efficiency.