Low-resistance Al-based reflectors for high-power GaN-based flip-chip light-emitting diodes

We report on the formation of high-quality p-type Al-based ohmic reflectors using Ag (3nm)∕indium tin oxide (ITO)(100nm) interlayers for use in high-power flip-chip light-emitting diodes (LEDs). The Ag∕ITO interlayers are first annealed at temperatures of 530 and 630°C for 1min in air, after which Al reflectors (200nm thick) are deposited and subsequently annealed at 330°C for 5min in a vacuum. It is shown that the annealed Ag∕ITO∕Al contacts give specific contact resistances as low as ∼10−5Ωcm−2 and reflectance of ∼85% at a wavelength of 460nm, which are much better than those of oxidized Ni∕Au schemes. LEDs fabricated with the annealed Ag∕ITO∕Al p-type electrodes give forward-bias voltages of 3.29–3.37V at injection current of 20mA.