High luminous efficacy green light-emitting diodes with AlGaN cap layer

Area of Science:

• Solid State Physics
• Materials Science
• Optoelectronics

Background:

• Indium Gallium Nitride (InGaN) based green light-emitting diodes (LEDs) are crucial for solid-state lighting.
• Achieving high luminous efficacy in green LEDs remains a significant challenge due to efficiency droop.

Purpose of the Study:

• To develop and demonstrate high luminous efficacy green LEDs.
• To investigate the impact of an Aluminum Gallium Nitride (AlGaN) cap layer on device performance.

Main Methods:

• Epitaxial growth of Al_0.30Ga_0.70N cap layer on patterned sapphire substrates using metal organic chemical vapor deposition (MOCVD).
• Fabrication and characterization of the green light-emitting diodes (LEDs).

Main Results:

• The fabricated green LEDs achieved a peak external quantum efficiency (EQE) of 44.3% and a peak luminous efficacy of 239 lm/W.
• At 20 mA (20 A/cm²), the devices exhibited a light output power of 14.3 mW, a forward voltage of 3.5 V, and an EQE of 30.2% at a 526.6 nm emission wavelength.
• These performance metrics represent some of the highest reported values for InGaN-based green LEDs.

Conclusions:

• The use of an AlGaN cap layer on patterned sapphire substrates significantly enhances the performance of green LEDs.
• The demonstrated devices offer a promising pathway towards highly efficient solid-state lighting solutions in the green spectrum.