Simple method to enhance positive bias stress stability of In-Ga-Zn-O thin-film transistors using a vertically graded oxygen-vacancy active layer

Ji Hoon Park, Yeong Gyu Kim, Seokhyun Yoon, Seonghwan Hong, Hyun Jae Kim

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25 Citations (Scopus)


We proposed a simple method to deposit a vertically graded oxygen-vacancy active layer (VGA) to enhance the positive bias stress (PBS) stability of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs). We deposited a-IGZO films by sputtering (target composition; In2O3:Ga2O3:ZnO = 1:1:1 mol %), and the oxygen partial pressure was varied during deposition so that the front channel of the TFTs was fabricated with low oxygen partial pressure and the back channel with high oxygen partial pressure. Using this method, we were able to control the oxygen vacancy concentration of the active layer so that it varied with depth. As a result, the turn-on voltage shift following a 10 000 s PBS of optimized VGA TFT was drastically improved from 12.0 to 5.6 V compared with a conventional a-IGZO TFT, without a significant decrease in the field effect mobility. These results came from the self-passivation effect and decrease in oxygen-vacancy-related trap sites of the VGA TFTs.

Original languageEnglish
Pages (from-to)21363-21368
Number of pages6
JournalACS Applied Materials and Interfaces
Issue number23
Publication statusPublished - 2014 Dec 10


All Science Journal Classification (ASJC) codes

  • Materials Science(all)

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