Appl. Phys. Lett. 102, 102108 (2013).
Byungsu Cho, Jaesang Lee, Hyungtak Seo, Hyeongtag Jeon.
Division of Materials Science and Engineering, Hanyang University, Seoul 133-791, Korea and
Samsung Display Co. Ltd., Tangjeong, Chungcheongnam-Do 336-741, Korea and
Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791, Korea and
Department of Materials Science and Engineering, Ajou University, Suwon 443-739, Korea.
We demonstrate a significant improvement in various electrical instabilities of amorphous indium gallium zinc oxide (a-IGZO) thin film transistor (TFT) by implanting Au nanoparticles (NPs) on the a-IGZO back-channel. This TFT showed the enhanced stability of threshold voltage (Vth) under ambient humidity, illumination stress, and a-IGZO thickness variation tests. Application of back-channel Au NPs to a-IGZO TFT is regarded to control the surface potential, to lead reversible carrier trap/injection, and to increase incident UV light absorption by local surface plasmon. Au NPs are formed by e-beam evaporation, and therefore, this technique can be applicable to the TFT manufacturing process.
© 2013 American Institute of Physics
Since amorphous indium gallium zinc oxide (a-IGZO) was introduced as a fascinating channel material for thin film transistors (TFTs) in 2004, a-IGZO TFTs have received enormous attention due to its superior properties of high mobility, low temperature deposition, and high transparency compared to those of conventional amorphous silicon for the flat panel display. Despite great advances of a-IGZO TFTs, their electrical instability and non-uniform electrical properties upon the large scale application have made it difficult to fully apply a-IGZO TFTs in industrial fabrication.A guarantee of device stability and uniform film quality under various external conditions is thus essential for application of a-IGZO TFTs in commercial fields. Our lab (advanced electronic/energy materials lab, aeem.ajou.ac.kr) has a strong research focus on improving a-IGZO channel to make technical breakthroughs in addressed problems. In the featured paper, we propose a special technique for a great stability improvement of a-IGZO TFTs using Au nanoparticle loading on the backside of TFT. The several factors affecting the electrical instability of a-IGZO TFTs include defect creation by prolonged gate bias, desorption/adsorption reaction between channel and the ambient, conditions of channel deposition process and the influence of illumination or temperature stress, resulting in the change of effective carrier density in active layer. Using the initial island-type growth mechanism of Au, we captured the proper E-beam evaporation deposition condition for 2 to 6 nm sized Au nanoparticle (NP) formation on a-IGZO backside. This process is totally compatible to the current mass-production processing in display industry, clearly distinguishable from wet-chemistry synthesis of Au NPs. The a-IGZO TFT with Au NPs showedthe enhanced stability of threshold voltage (Vth) under humidity ambient, illumination stress, and a-IGZOthickness variation tests. Application of back-channel Au NPs to a-IGZO TFT is regarded to control thesurface potential, lead to reversible carrier trap/injection, increase incident UV light absorption by localsurface plasmon.To the best of our knowledge, this is a first remarkable report for improvement of stability byapplying metal nanoparticles. Au NPs on the a-IGZO back-channel can effectively improve the stabilityof Vth without other passivation or treatment process. Therefore, this technique is potentially applicable tothe TFT manufacturing process. Also, this report may be the foundation to study the effect of othernanoparticles in the oxide TFT. Our group is about to report another remarkable data for about 4-fold improvement in carrier channel mobility in a-IGZO TFT using homogeneous imbedded conducting layer.