Effects of film thickness and annealing temperature on the specific contact resistivity and the lransmittance of the IZO layers grown on p-GaN by roll-to-roll sputtering

We report on the characteristics of indium-oxide-doped ZnO (IZO) ohmic contact to p-GaN. The IZO ohmic contact layer was deposited on p-GaN by a Roll-to-Roll (RTR) sputter method. IZO contact film with a thickness of 360, 230 and 100 nm yielded an ohmic contact resistance of 4.70×10^-4, 5.95×10^-2, 4.85× 10^-1 ωcm² on p-GaN when annealed at 600°C for 1 min under a nitrogen ambient, respectively. While the transmittance of IZO film with a thickness of 360 nm slightly increased in the wavelength range of 380-800 nm after annealing, the transmittance rapidly increased up to 80% after annealing at 600°C in the wavelength range of 380-430 nm because the crystallization of IZO film and created Ga vacancies near the p-GaN surface region were affected by the annealing. These results indicate that ohmic contact resistance and transmittance of the IZO films improved.