The Study on Reliability of Compound Thin Film Transistors

• Main Authors: Chien-Feng Lee, 李建鋒
• Other Authors: Chiung-Wei Lin
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/30606007519327362635

碩士 === 大同大學 === 光電工程研究所 === 94 === We had proposed previously a μc-Si:H TFTs with vertical a-Si:H offset structure (compound TFT) to improve the performance of active-matrix organic light emitting diode (AMOLED). It was proved previously that this proposed compound TFTs structure presenting not only high ON-state current but also low OFF-state current, which was similar to that of a-Si:H TFTs. In this thesis, the reliability of compound TFT was studied. In high-field stress test, various bias stresses on gate electrode were performed on the compound TFTs, and the results showed that the instability in compound TFTs was less than that in a-Si:H TFT without regarding the polarity of the VGS. A new mechanism named “H atom compensation effect” was proposed resulting in an improvement in the sub-threshold swing of the compound TFT when compound TFT was tested in the negative gate bias stress. This mechanism resulted from the released H atoms, which caused by the breaking of weak Si-H bonds in the a-Si:H offset layer, and they could be injected into the channel resulting in the reduction of the states located in the gate insulator/channel interface under negative gate bias stress. It improved the operation of compound TFT. In the aging test, the lifetime of the compound TFT was stopped after about 4,450sec in the condition VGS=20V while VDS=80V. Additionally, the leakage current decreased gradually with the time due to there was gradually not enough space in the insulator for carriers to hop. All the experimental results in this thesis implied that the compound TFTs showed good reliability as compared with conventional a-Si:H TFTs. It was possible that the crystallinity of the channel layer in compound TFT was much better than that in a-Si:H TFT. Therefore, the compound TFTs may be a good candidate for the practical AMOLED operation.