Development of high performance green c-plane III-nitride light-emitting diodes

Area of Science:

• Semiconductor Physics
• Materials Science
• Optoelectronics

Background:

• Green light-emitting diodes (LEDs) are crucial for displays and lighting.
• Improving the efficiency and performance of InGaN/GaN quantum wells (QWs) is an active research area.

Purpose of the Study:

• To investigate the impact of an Aluminum Gallium Nitride (AlGaN) cap layer within the active region of green c-plane LEDs.
• To optimize AlGaN cap layer thickness and Gallium Nitride (GaN) barrier growth temperature for enhanced LED performance.

Main Methods:

• Fabrication of green c-plane LEDs with varying AlGaN cap layer thicknesses and GaN barrier growth temperatures.
• Experimental characterization and simulation of LED efficiency, electrical performance, and material morphology.

Main Results:

• An AlGaN cap layer thickness of approximately 2 nm and a GaN barrier growth temperature ~75°C higher than the InGaN QW growth temperature were found to be optimal.
• Optimized conditions yielded peak external quantum efficiency (EQE) of 40.7% at 3 A/cm².
• At 20 A/cm², optimized LEDs demonstrated 13.8 mW output power, 29.5% EQE, 3.5 V forward voltage, and 529.3 nm emission wavelength.

Conclusions:

• The AlGaN cap layer plays a significant role in the efficiency and electrical characteristics of green LEDs.
• Precise control over AlGaN cap thickness and barrier growth temperature is essential for achieving high-efficiency, low-voltage, and morphologically stable green LEDs.