Effect of depth of traps in ZnO polycrystalline thin films on ZnO-TFTs performance

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• 作者：Maria I. Medina-Montes^a ; ^{lebasi_tresm@hotmail.com" class="auth_mail" title="E-mail the corresponding author} ; Leonardo A. Baldenegro-Perez^b ; Raul Sanchez-Zeferino^c ; Lizeth Rojas-Blanco^a ; Marcelino Becerril-Silva^d ; Manuel A. Quevedo-Lopez^b ; Rafael Ramirez-Bon^a
• 关键词：Zinc oxide thin films ; Rf magnetron sputtering ; Thin film transistor ; Traps ; TSC ; PL
• 刊名：Solid State Electronics
• 出版年：2016
• 出版时间：September 2016
• 年：2016
• 卷：123
• 期：Complete
• 页码：119-123
• 全文大小：946 K

文摘

ZnO thin films were processed by radio frequency magnetron sputtering at room temperature on p-Si/SiO₂ substrates under pure argon (Ar:O₂ = 100:0 vol.%) and argon–oxygen mixture (Ar:O₂ = 99:1 vol.%) gas environment. Morphological, optical and electrical characteristics of the ZnO films are reported, and they show a clear relationship with the gas mixture employed for the sputtering process. Scanning Electron Microscopy revealed the formation of grains of 15.3 and 19.9 nm average sizes and thicknesses of 59 nm and 82 nm for films growth in pure argon and argon–oxygen, respectively. Photoluminescence measurements at room temperature showed the violet emission band (centered at 3 eV) which was only detected in the ZnO film grown under pure argon. From thermally stimulated conductivity measurements two traps with 0.27 and 0.14 eV activation energies were identified for films grown in pure argon and argon–oxygen mixture, respectively. The trap at 0.27 eV is associated with a level located below the conduction band edge and it is supported by the PL band centered at 3 eV. Both types of ZnO films were used as the active channel layer in thin film transistors with thermal SiO₂ as gate dielectric. Field effect mobility, threshold voltage and current ratio were improved in the devices with ZnO channel deposited with the argon–oxygen mixture (99% Ar/1% O₂ vol.). Threshold voltage decreased from 25 V to 15 V, field effect mobility and current ratio increased from 0.8 to 2.4 cm²/Vs and from 10² to 10⁶, in that order.