Al-based Ohmic reflectors with low leakage currents and high reflectance for p-GaN flip-chip processes

The authors report the improvement of InGaN∕GaN light-emitting diodes on Al reflectors, commonly used as n-type GaN contacts. A Cu-doped indium oxide (CIO) (5nm)/indium tin oxide (ITO) (380nm) interlayer was deposited and annealed at 500°C, after which an Al (400nm)∕Ti–W (30nm) layer was sputtered on the ITO interlayer to reflect the light. The reflectance of CIO∕ITO∕Al∕Ti–W was ∼92% at 460nm, higher than that of the popular Ni∕Ag∕Pt scheme, and the forward voltage was 3.2–3.3V, similar to that of the Ni∕Ag∕Pt contact. Furthermore, the mean leakage current of CIO∕ITO∕Al∕Ti–W was 0.12μA, much lower than 0.54μA of Ni∕Ag∕Pt at −5V.