Vertical GaN light-emitting diodes fabricated by laser lift-off technique

In order to improve the electrical characteristic and light output power of GaN-based light-emitting diodes (LEDs), GaN-based LEDs are separated from sapphire substrates by laser lift-off (LLO) technique using KrF excimer laser with 400mJ/cm² energy density. The free-standing GaN-based LEDs are transferred to Si substrates by Sn/Au fusion bonding at 300°C, forming the vertical GaN-based LEDs on Si. The electrical and optical characteristics of the samples are investigated. The results show that the forward voltage of GaN-based LEDs on Si and on sapphire is 3.27V and 3.68V respectively at 110mA, and the output power of vertical GaN-based LEDs keeps increasing up to 560mA free of saturation because of the high electrical and thermal conductivity of Si substrates.