By reducing the thickness of the quantum wells down to a single atomic layer and tuning their composition, the team achieved a spectral shift down to 235 nm, with room-temperature internal quantum efficiencies exceeding 50% at this wavelength. The study reveals that this efficiency enhancement originates from strong in-plane carrier localization, which reduces carrier diffusion toward non-radiative defects and promotes radiative recombination.
In nitride-based deep-UV emitters, the polarization of the emitted light is a key factor governing light extraction efficiency. In this work, shorter emission wavelengths are achieved using ultrathin quantum wells with a high gallium content. This approach allows transverse-electric polarization (with the electric field parallel to the sample surface) to be maintained down to shorter wavelengths than in conventional aluminum-rich structures, where transverse-magnetic polarization (with the electric field perpendicular to the surface) typically dominates. As a result, this design is expected to improve light extraction efficiency in practical devices.
Figure : (Left) Evolution of the emission spectrum of GaN and AlGaN quantum wells as a function of quantum-well thickness. Reducing the well thickness down to the one-atomic-layer (1 ML) regime produces a strong blueshift of the emission, enabling deep-UV wavelengths down to 235 nm. (Center) Polar plots of the luminescence intensity showing the polarization characteristics of the emission for representative samples emitting at different wavelengths. (Right) Transmission electron microscopy image showing GaN quantum wells with a thickness of 1 ML.
©CEA-Irig/PHELIQS/NPSC
A systematic comparison with other nitride nanostructures grown in the same reactor shows that ultrathin quantum wells outperform both quantum dots and nanowire heterostructures for emission below 240 nm, highlighting their potential for next-generation UVC light sources.
These results open promising perspectives for the development of compact, mercury-free UV emitters for environmental and health-related applications.