A study of transparent indium tin oxide (ITO) contact to p-GaN

Abstract In this study, indium tin oxide (ITO) thin film was evaporated on Mg-doped p-GaN layers with low 10 17 /cm 3 , grown by metalorganic chemical vapor deposition (MOCVD) on (0001) sapphire wafers, and its contact properties were investigated. The sheet resistance ( R S ) of the evaporated ITO films was several kΩ/□ before the annealing but the sheet resistance decreased to 40–50 Ω/□ after the annealing in N 2 using a rapid thermal annealing (RTA) system. I – V characteristics and contact resistivities of the evaporated ITO on p-type GaN were investigated as a function of substrate treatment, annealing time, and annealing temperature. The results showed that, in optimized conditions, the ITO contacts with the resistance in the range of low 10 −1 Ω cm 2 could be obtained, and which is probably applicable as the ohmic contact for GaN-based light emitting diodes. Also, at these conditions, the measured optical transmittances of ITO film were above 90% at a wavelength of 420 nm (blue).