High Mobility and Photo‐Bias Stable Metal Oxide Thin‐Film Transistors Engineered by Gradient Doping

Abstract

AbstractDoping of oxygen‐deficient binder is an efficient way to alleviate the photo‐bias instability issue of oxide thin‐film transistors (TFTs). However, almost all dopants are working as electron suppressors and degrading mobility. Here we report an effective three‐level O‐anti|O|O‐N (OI|OII|N) gradient doping solution to overcome the adverse mobility‐stability trade‐off in N‐doped InGaZnO (IGZO:N) TFTs. 100 nm‐thick IGZO:OI|IGZO:OII|IGZO:N (IGZO:OI|OII|N) junctionless channel layers are fabricated by varying the partial pressures of oxygen and nitrogen doping gases. Best balance between improved performance and negligible degraded stability is first engineered by reducing the back‐channel IGZO:N depth close to the theoretical diffusion length of photo‐excited holes and forming two‐level graded IGZO:OII|N (40 nm|60 nm) TFTs. Much improved performance and comparable stability are further induced by incorporating ~1.5 nm percolation conduct IGZO:OI at the front‐channel to enhance accumulation. The three‐level graded IGZO:OI|OII|N TFTs exhibit high mobility (34.25 cm2 V−1 s−1) and good photo‐bias stability (∆Vth = −0.85 V@10 000 cd m−2, 3.0 h), which are 2~5‐fold superior to those of the controlled two‐level graded IGZO:OI|N TFTs, IGZO:OII|N TFTs, and homogeneous IGZO:OII TFTs, IGZO:N TFTs. The fabrication of high mobility and photo‐bias stable IGZO TFTs paves the way to future high‐performance oxide electronics.