Highly low resistance and transparent Ni/ZnO ohmic contacts to p-type GaN

Song, June O; Kim, Kyoung-Kook; Park, Seong-Ju; Seong, Tae-Yeon
July 2003
Applied Physics Letters;7/21/2003, Vol. 83 Issue 3, p479
Academic Journal
We report on a promising Ni (5 nm)/Al-doped ZnO (AZO) (450 nm) metallization scheme for low resistance and transparent ohmic contacts to p-GaN (5 × 10[SUP17]cm[SUP-3]). It is shown that the as-deposited Ni/AZO contact shows a nonohmic characteristic due to the insulating nature of the as-deposited AZO. However, annealing the contacts at 450 and 550 °C for 2 min in air ambient results in linear current-voltage characteristics, giving a specific contact resistance of 1.01 × 10[SUP-5] and 8.46 × 10[SUP-6] V cm[SUP2] respectively. It is further shown that annealing the contact at 550 °C for 5 min produces a specific contact resistance of 6.23 × 10[SUP-6] V cm[SUP2]. The light transmittance of the contacts annealed at 550 °C for 2 min is measured to be higher than 76% at wavelengths in the range of 400-550 nm. It is shown that the Ni/AZO contact could be a suitable scheme for high-performance optical devices.


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