Enhancing the efficiency of InGaN-based micro-LEDs using indium tin oxide p-electrodes

Area of Science:

• Optoelectronics
• Materials Science
• Semiconductor Devices

Background:

• Indium gallium nitride (InGaN)-based micro-light-emitting diodes (micro-LEDs) are crucial for advanced display and lighting applications.
• Conventional micro-LEDs often use opaque metal p-electrodes (e.g., Cr/Pt/Au), which limit light extraction efficiency due to absorption.

Purpose of the Study:

• To investigate the replacement of opaque metal p-electrodes with transparent indium tin oxide (ITO) p-electrodes in InGaN-based micro-LEDs.
• To enhance the light output power and external quantum efficiency (EQE) of micro-LEDs.

Main Methods:

• Fabrication of green micro-LED arrays (20x20 µm² and 50x50 µm²) utilizing ITO p-electrodes.
• Comparison of optical and electrical performance metrics (light output power, EQE) between devices with ITO and conventional metal p-electrodes.
• Characterization of ITO p-electrode properties, including transmittance and resistivity.

Main Results:

• ITO p-electrodes demonstrated high transmittance (∼80%) across the visible spectrum and low resistivity.
• Micro-LEDs with ITO p-electrodes showed a 1.20-1.25 times improvement in light output power compared to metal p-electrode devices.
• On-wafer EQE reached 7.36% for ITO devices, a significant increase from 5.98%-6.16% for metal devices at current densities ≤1.6 A/cm².

Conclusions:

• Replacing opaque metal p-electrodes with transparent ITO p-electrodes is an effective strategy for enhancing micro-LED light output and EQE.
• The ITO p-electrode approach is compatible with red, green, and blue micro-LED configurations, offering a universal performance enhancement solution.