Abstract
We numerically investigated the performance of N-polar AlGaN-based ultraviolet (UV) light-emitting diodes (LEDs) with different Al contents in quantum wells (QWs) and barriers. We found that N-polar structures could improve the maximum internal quantum efficiency (IQE) and suppress the efficiency droop, especially for deep-UV LEDs. Compared to metal-polar LEDs, N-polar ones retained higher IQE values even when the acceptor concentrations in the p-layers were one order of magnitude lower. The enhanced performance originated from the higher injection efficiencies of N-polar structures in terms of efficient carrier injection into QWs and suppressed electron overflow at high current densities.
Highlights
AlGaN-based ultraviolet (UV) light-emitting diodes (LEDs) have attracted considerable attention to replace toxic mercury-based UV lamps
The external quantum efficiency (EQE) of state-of-art AlGaN-based deep-UV LEDs is 20.3% [10], so there is a need for further improvements compared to commercial InGaN-based visible LEDs [11]
When the difference in Al content between barriers and quantum wells (QWs) (XB-XW) was varied from 0.1 to 0.2, the EL peak shifts were small for both types of LEDs
Summary
AlGaN-based ultraviolet (UV) light-emitting diodes (LEDs) have attracted considerable attention to replace toxic mercury-based UV lamps. N-polar devices have demonstrated enhanced carrier injection in both simulations and experiments [20,21] This advantage of N-polar structures was demonstrated to be possible to suppress the efficiency droop in visible InGaN-based LEDs [22], and achieved a flat EQE curve up to 400 A/cm even without electron blocking layers [23]. Unlike N-polar InGaN visible LEDs, N-polar AlGaN UV LEDs grown at high temperature are promising to reduce the impurity concentrations and obtain a better luminescence compared to metal-polar devices. The X-ray rocking curve full width half maximums (FWHMs) were 203 arcsec and 389 arcsec for (002) and (102) reflections, respectively These FWHMs demonstrated that high-quality N-polar AlN templates were possible to be achieved by optimal growth conditions.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
