Electrical and optical characteristics of high power vertical GaN light-emitting diodes on Si substrates

High power vertical GaN-based light-emitting diodes (LEDs) on Si substrates are fabricated by wafer bonding and laser lift-off (LLO) technique. The GaN-based LEDs are grown on sapphire (0001) substrates by metalorganic chemical vapour deposition (MOCVD). GaN-based LEDs are joined to Si receptor substrates by Sn/Au fusion bonding at the temperature of 300 degC in flowing nitrogen ambient. KrF excimer laser with 400 mJ/cm² energy density is used to irradiate GaN-based LEDs from transparent sapphire substrates to separate the samples from sapphire, forming GaN-based LEDs/Sn/Au/Si structure. Using the samples grown on the same wafer, the electrical and optical characteristics of the GaN-based LEDs on sapphire and on Si are investigated. At 20 mA, the forward voltages of GaN-based LEDs on Si and sapphire are 3.1V and 3.3 V respectively. At high operation current 110 mA, the I-V characteristic of vertical strcture GaN-based LEDs on Si can be improved much more greatly. The light output power of GaN-based LEDs on Si keeps increasing up to 560 mA without any power saturation.