Residual Al Adatoms Driven Epitaxy of AlGaN QWs for High-Performance UV LEDs

AlGaN-based ultraviolet (UV) light-emitting diodes (LEDs) experience a notable reduction in efficiency within the 280-330 nm wavelength range, known as the "UVB gap". Given the extensive applications of UV LEDs in this wavelength range, it is imperative to bridge this efficiency gap. In this study, a strategy facilitated by the presence of residual Al adatoms is introduced to simultaneously improve the integration of Ga-adatoms and the migration of Al/Ga-adatoms during the growth of low-Al-composition AlGaN quantum wells (QWs) even at high temperatures comparable to those used for high-Al-composition AlGaN quantum barriers. This growth strategy enables the epitaxy of high-quality AlGaN QWs with a wide tunable emission wavelength range across the UVB gap. Utilizing this approach, high-efficiency UV LEDs that effectively bridge the UVB gap are developed. Furthermore, benefiting from this QWs growth configuration, these UV LEDs exhibit an exceptionally long L70 lifetime, marking a significant step forward in the growth technology of AlGaN QWs and expanding the application possibilities of UV LEDs.