Wafer-Scale Characterization of 1692-Pixel-Per-Inch Blue Micro-LED Arrays with an Optimized ITO Layer

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Devices

Background:

• Micro-light-emitting diodes (micro-LEDs) are promising for high-resolution displays.
• Indium tin oxide (ITO) is a critical transparent conductive material in micro-LED fabrication.
• Achieving uniform electrical properties across large-scale arrays remains a challenge.

Purpose of the Study:

• To fabricate wafer-scale blue micro-LED arrays with high pixel density.
• To investigate the impact of different indium tin oxide (ITO) deposition methods on micro-LED performance.
• To evaluate the suitability of optimized ITO for advanced display applications like augmented reality (AR) and virtual reality (VR).

Main Methods:

• Fabrication of wafer-scale blue micro-LED arrays with 12 μm pixel size and 15 μm pitch.
• Optimization of e-beam-deposited ITO (E-ITO) and sputter-deposited ITO (S-ITO) films.
• Characterization of ITO film morphology, resistivity, and micro-LED forward voltage (V_F).

Main Results:

• Micro-LED arrays achieved a pixel density of 1692 pixels per inch.
• E-ITO films resulted in lower V_F (2.82 V single pixel) compared to S-ITO (3.50 V single pixel).
• Optimized E-ITO demonstrated highly uniform V_F variation (0.09 V across five regions).

Conclusions:

• E-beam-deposited ITO is superior to sputter-deposited ITO for blue micro-LEDs due to lower V_F and reduced damage.
• The exceptional V_F uniformity of E-ITO is ideal for mass production of micro-LED displays.
• This advancement addresses limitations of organic LEDs for AR/VR applications.