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

Doping 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 vertical bar O vertical bar O-N (O-I vertical bar O-II vertical bar N) gradient doping solution to overcome the adverse mobility-stability trade-off in N-doped InGaZnO (IGZO:N) TFTs. 100 nm-thick IGZO:O-I vertical bar IGZO:OII vertical bar IGZO:N (IGZO:O-I vertical bar O-II vertical bar 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:O-II vertical bar N (40 nml60 nm) TFTs. Much improved performance and comparable stability are further induced by incorporating similar to 1.5 nm percolation conduct IGZO:O-I at the front-channel to enhance accumulation. The three-level graded IGZO:O-I vertical bar O-II vertical bar N TFTs exhibit high mobility (34.25 cm(2) V(-1)s(-1)) and good photo-bias stability (Delta V-th = -0.85 V@10000 cd m(-2), 3.0 h), which are 2 similar to 5-fold superior to those of the controlled two-level graded IGZO:O-I vertical bar N TFTs, IGZO:O-II vertical bar N TFTs, and homogeneous IGZO:O-II TFTs, IGZO:N TFTs. The fabrication of high mobility and photo-bias stable IGZO TFTs paves the way to future high-performance oxide electronics.