Light extraction efficiency improvement by multiple laser stealth dicing in InGaN-based blue light-emitting diodes

Area of Science:

• Materials Science
• Optoelectronics
• Laser Processing

Background:

• Improving light extraction efficiency (LEE) is crucial for InGaN-based light-emitting diodes (LEDs).
• Conventional dicing methods can limit LED performance and introduce defects.
• Laser stealth dicing (LSD) offers a non-contact approach for precise material processing.

Purpose of the Study:

• To introduce and evaluate a multiple laser stealth dicing (multi-LSD) method.
• To enhance the light output power (LOP) and LEE of InGaN LEDs.
• To investigate the impact of multi-LSD on sapphire substrate morphology and thermal effects.

Main Methods:

• Development of a multi-LSD technique using a picosecond (Ps) laser.
• Fabrication of InGaN LEDs utilizing the multi-LSD process.
• Comparison of multi-LSD with conventional nanosecond (Ns) laser scribing and single-LSD methods.
• Analysis of light output power (LOP) and substrate sidewall morphology.
• Numerical simulations to assess thermal damage to multiple quantum wells (MQWs).

Main Results:

• The multi-LSD method improved LOP by 26.5% compared to Ns laser scribing.
• A 11.2% LOP enhancement was observed compared to single-LSD processed LEDs.
• Increased side emission resulted from large-area roughened sapphire sidewalls created by multi-LSD.
• Numerical simulations confirmed minimal thermal damage to the MQWs.

Conclusions:

• The multi-LSD technique is an effective method for enhancing InGaN LED performance.
• The roughened sidewalls generated by multi-LSD significantly contribute to improved light extraction.
• This advanced dicing process offers a promising route for high-efficiency LED fabrication with reduced thermal impact.