Performance comparison of flip-chip blue-light microLEDs with various passivation

Area of Science:

• Optoelectronics
• Materials Science
• Semiconductor Devices

Background:

• Micro-LEDs (μLEDs) are crucial for advanced display technologies.
• Optimizing μLED performance requires effective passivation strategies to minimize leakage current and enhance efficiency.
• Current passivation methods face challenges in achieving uniform coverage and robust protection, especially for small-sized devices.

Purpose of the Study:

• To investigate the impact of a double-layer passivation process on micro-LED performance.
• To compare the efficacy of single-layer SiO2 passivation versus a double-layer Al2O3/SiO2 passivation.
• To analyze the effects on leakage current, light output power, external quantum efficiency (EQE), and emission uniformity.

Main Methods:

• Fabrication of μLED arrays in various sizes (5-50 μm) using flip-chip bonding.
• Implementation of two passivation techniques: single-layer SiO2 (via PECVD) and double-layer Al2O3/SiO2 (ALD/PECVD).
• Characterization of μLED performance, including leakage current, light output power, EQE, and emission patterns using ImageJ software.

Main Results:

• The double-layer passivation significantly reduced leakage current by three orders of magnitude for 5 μm μLEDs.
• Higher light output power was observed across all μLED sizes with the double-layer passivation.
• An exceptional EQE of 21.9% was achieved for 5 μm μLEDs, a 4.4-fold improvement over single-layer passivation.
• More uniform light emission patterns were observed for 5 μm μLEDs using the double-layer method.

Conclusions:

• The double-layer Al2O3/SiO2 passivation offers superior protection and coverage compared to single-layer SiO2.
• This advanced passivation technique dramatically improves μLED performance, especially for small-sized devices.
• The findings pave the way for more efficient and reliable micro-LED displays.