Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 100: ZnO and its relatives

HL 100.6: Talk

Friday, March 20, 2015, 11:00–11:15, EW 203

Selective Back Channel Passivation of ZnO TFTs Utilizing Oxiranes — •Marlis Ortel, Nataliya Kalinovich, Gerd-Volker Röschenthaler, and Veit Wagner — Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany

Zinc oxide layers of 10nm film thickness were deposited by spray pyrolysis as active layer in TFT structures. They were utilized to investigate the influence of the surface at the back channel on the charge transport processes in ZnO TFTs by detailed IV analysis. A strong but reversible increase of shallow and deep trap states was found when the material was exposed to humid atmosphere. This results in a decrease in mobility, increase in hysteresis and shift of the threshold voltage during gate bias stress due to coulomb interaction of surface and active channel charges.

Oxiranes were selectively bound to hydroxyl groups at the metal oxide surface to gain information about the active sides at the surface which induce the change of the electronic surface structure. The binding of hexafluoropropylene oxide self-assembled monolayer (SAM) to the surface caused a significant decrease in hysteresis by a factor of 4. Furthermore, no shift of the on-set under negative gate bias stress was observed after oxirane treatment and the mobility remained stable. We conclude that hydroxyl surface groups act as active sides to induce mainly deep trap levels at the back channel of ZnO TFTs in humid atmosphere.