P-type oxide-based thin film transistors produced at low temperatures

Abstract

P-type thin-film transistors (TFTs) using room temperature sputtered tin and copper oxide as a transparent oxide semiconductor have been produced on rigid and paper substrates. The SnOx films shows p-type conduction presenting a polycrystalline structure composed with a mixture of tetragonal β-Sn and α-SnOx phases, after annealing at 200 °C. These films exhibit a hole carrier concentration in the range of ≈ 1016-1018 cm-3, electrical resistivity between 101-102 Ωcm, Hall mobility of 4.8 cm2/Vs, optical band gap of 2.8 eV and average transmittance ≈ 85 % (400 to 2000 nm). Concerning copper oxide CuxO thin films they exhibit a polycrystalline structure with a strongest orientation along (111) plane. The CuxO films produced between an oxygen partial pressure of 9 to 75% showed p-type behavior, as it was measured by Hall effect and Seebeck measurements. The bottom gate p-type SnOx TFTs present field-effect mobility above 1.24 cm2/Vs (including the paper p-type oxide TFT) and an on/off modulation ratio of 103 while the CuxO TFTs exhibit a field-effect mobility of 1.3×10-3 cm2/Vs and an on/off ratio of 2×102.