Performance enhancement of InGaN light-emitting diodes by laser lift-off and transfer from sapphire to copper substrate

Laser lift-off technique was employed to carry out transfer of prefabricated InGaN multiple-quantum-well light-emitting diodes (LEDs) from sapphire onto Cu substrate. Silver epoxy was used as the bonding material. Characterization results showed tremendous device improvements in terms of maximum allowable current, light output power, and reliability from the use of conductive Cu substrate. LEDs on Cu could withstand a maximum current of 530 mA before breakdown while those on sapphire could only withstand 350 mA. At 40 mA, light output power of LEDs on sapphire and Cu was 0.74 and 0.95 mW, respectively. In addition, reliability test at constant current of 300 mA showed improvement in light output power for LEDs on Cu whereas LEDs on sapphire suffered deterioration with time.

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