10.4% external quantum efficiency 294 nm UV LEDs at 20 A/cm² with a fully transparent tunnel junction

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Development of efficient germicidal ultraviolet light-emitting diodes (UV LEDs) is crucial for applications like disinfection and sterilization.
• Transparent tunnel junctions (TJs) are essential components for enhancing UV LED performance by facilitating current spreading and reducing voltage drop.
• Metalorganic chemical vapor deposition (MOCVD) is a key technique for fabricating high-quality semiconductor devices.

Purpose of the Study:

• To demonstrate an all-MOCVD grown, fully transparent tunnel junction (TJ) germicidal UV LED.
• To optimize the MOCVD growth process for improved LED performance.
• To investigate the impact of specific AlGaN compositions and structures on TJ and UV LED characteristics.

Main Methods:

• Utilized all-metalorganic chemical vapor deposition (MOCVD) for device fabrication.
• Employed a lightly doped n-AlGaN contact layer to enable rapid MOCVD growth optimization.
• Designed an optimal tunnel junction structure comprising p++/n++-AlGaN layers and a short-period superlattice (SPSL) of AlGaN/AlGaN.

Main Results:

• Achieved a peak external quantum efficiency (EQE) of 12.1% for a 294 nm TJ UV LED.
• Observed high EQE values of 10.4% at 20 A/cm² and 9.1% at 35 A/cm².
• Recorded an excess voltage of 1.5 V at 1 A/cm², indicating efficient current transport.

Conclusions:

• Successfully demonstrated a fully transparent TJ UV LED grown entirely by MOCVD.
• The optimized AlGaN-based TJ structure and MOCVD growth conditions significantly enhance UV LED performance.
• This advancement holds promise for efficient and reliable germicidal UV light sources.