Increasing light extraction efficiency for UV LEDs with a low coverage p-GaN hole injection layer

Area of Science:

• Optoelectronics
• Semiconductor Physics
• Materials Science

Background:

• Ultraviolet (UV) Light Emitting Diodes (LEDs) are crucial for various applications, but light extraction efficiency remains a challenge.
• Improving deep UV emission, particularly in the UVB spectrum (280-315 nm), requires novel approaches to overcome internal optical losses.

Purpose of the Study:

• To investigate the impact of ultrathin low-coverage p-GaN hole injection islands on light extraction in UV LEDs.
• To achieve world-record efficiencies for AlGaN-based UVB LEDs operating at 300 nm and 310 nm.

Main Methods:

• Fabrication of UV LEDs utilizing p-GaN islands on the top surface.
• Optimization of p-GaN island parameters including density, size, thickness, and doping concentration.
• Characterization of device performance, focusing on external quantum efficiency (EQE) and wall plug efficiency (WPE) under continuous wave (CW) operation.

Main Results:

• Demonstrated world-record UVB AlGaN UV LEDs emitting at 300 nm and 310 nm.
• A 300 nm device achieved a peak CW external quantum efficiency (EQE) of 18.9% and a peak CW wall plug efficiency (WPE) of 16.8%.
• A 310 nm device achieved a peak CW EQE of 20.3% and a peak CW WPE of 15.4%, with significant EQE maintained at high current densities (20 A/cm²).

Conclusions:

• Ultrathin low-coverage p-GaN islands are an effective strategy for enhancing light extraction in UV LEDs.
• The optimized p-GaN island approach enables record-breaking performance for UVB AlGaN LEDs.
• This method holds significant promise for advancing deep UV optoelectronic device technology.