Blue inorganic light emitting diode on flexible polyimide substrate using laser lift-off process

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Device Fabrication

Background:

• Flexible electronics are gaining traction, requiring adaptable fabrication methods for optoelectronic devices.
• Gallium Nitride (GaN) based inorganic light-emitting diodes (ILEDs) are crucial for lighting and displays.
• Traditional GaN ILED fabrication on rigid substrates limits applications in flexible form factors.

Purpose of the Study:

• To demonstrate a viable fabrication process for blue GaN ILEDs on flexible polyimide (PI) substrates.
• To utilize the laser lift-off (LLO) technique for efficient GaN film transfer.
• To evaluate the electrical performance of GaN ILEDs fabricated on both rigid and flexible substrates.

Main Methods:

• GaN epi-structure growth on a patterned sapphire wafer.
• Temporary bonding of GaN samples to a flexible polyimide substrate using silver epoxy.
• Laser lift-off (LLO) using a KrF excimer laser (248 nm) for GaN film separation from sapphire.
• Device fabrication and current-voltage (I-V) performance characterization on both silicon and polyimide substrates.

Main Results:

• Successful demonstration of the laser lift-off (LLO) process for transferring the entire GaN LED film.
• GaN ILEDs fabricated on flexible polyimide substrates exhibited comparable I-V performance to those on rigid silicon.
• The optimized LLO method proved effective for GaN film transfer to flexible substrates.

Conclusions:

• The demonstrated laser lift-off (LLO) process is a key enabler for fabricating high-performance GaN ILEDs on flexible substrates.
• This method allows for the integration of GaN ILEDs into flexible electronic applications without sacrificing electrical properties.
• The findings pave the way for advanced flexible optoelectronic devices and displays.