In₂O₃‐Based Transparent Conducting Oxide Films with High Electron Mobility Fabricated at Low Process Temperatures

Abstract

The emerging technological demands for high‐efficiency solar cells and flexible optoelectronic devices have stimulated research on transparent conducting oxide (TCO) electrodes. High‐mobility TCOs are needed to achieve high conductivity with improved visible and near‐infrared transparency; however, the fabrication of TCO films on heat‐sensitive layers or substrates is constrained by the trade‐off between fabrication temperatures and TCO properties. Historically, Sn‐doped indium oxide and amorphous In–Zn–O have been used as standard TCOs to achieve high mobility using low fabrication temperatures. However, two polycrystalline In 2 O 3 films with significantly higher mobilities have recently been reported: i) polycrystalline ( poly ‐) In 2 O 3 films doped with metal (Ti, Zr, Mo, or W) impurities instead of Sn exhibit mobilities greater than ≈80 cm 2 V −1 s −1 even when grown at low temperatures and ii) solid‐phase crystallized ( spc ‐) H‐doped In 2 O 3 (In 2 O 3 :H) and In 2 O 3 :Ce,H films exhibit mobilities greater than 100 cm 2 V −1 s −1 when processed at low temperatures of 150–200 °C. Here, poly ‐In 2 O 3 , In 2 O 3 :W, and In 2 O 3 :Ce films and spc ‐In 2 O 3 :H, In 2 O 3 :W,H, and In 2 O 3 :Ce,H films are fabricated. Comparative studies of these films reveal the effect of the i) metal dopant species; ii) metal and hydrogen codoping; and iii) solid‐phase crystallization process on the resultant transport properties.