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