Effects of post-annealing on (110) Cu2O epitaxial films and origin of low mobility in Cu2O thin-film transistor

✍ Scribed by Matsuzaki, Kosuke ;Nomura, Kenji ;Yanagi, Hiroshi ;Kamiya, Toshio ;Hirano, Masahiro ;Hosono, Hideo

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 687 KB
• Volume: 206
• Category: Article
• ISSN: 0031-8965
• DOI: 10.1002/pssa.200881795

✦ Synopsis

Abstract

We grew epitaxial (110) Cu~2~O films on (110) MgO substrates toward high‐mobility p‐channel oxide thin‐film transistors (TFTs). The (110) Cu~2~O films exhibited high Hall mobilities ∼90 cm^2^(Vs)^−1^ comparable to those of high‐quality single‐crystals, which were obtained in a narrow growth condition for 650 nm‐thick films. TFTs using the epitaxial (110) Cu~2~O channels exhibited p‐channel operation, but the field‐effect mobilities and the on‐to‐off drain current ratio were far from satisfaction (∼0.04 cm^2^(Vs)^−1^ and ∼2, respectively). In order to investigate the origin of the poor mobility, the films were subjected to post‐deposition annealing under various oxygen partial pressures (P~O2−A~ = 0.65–10^−3^ Pa). Optical measurements revealed that subgap states exist in all the films and their amounts were increased by post‐deposition annealing irrespective of P~O2−A~. The subgap density of states estimated by the optical analyses are consistent roughly with that estimated from the TFT mobility.