Polycrystalline InGaO Thin‐Film Transistors with Coplanar Structure Exhibiting Average Mobility of ≈78 cm<sup>2</sup>V<sup>‐1</sup>s<sup>‐1</sup>and Excellent Stability for Replacing Current Poly‐Si Thin‐Film Transistors for Organic Light‐Emitting Diode Displays
Md. Hasnat Rabbi, Suhui Lee, Daichi Sasaki, Emi Kawashima, Yuki Tsuruma, Jin Jang
Abstract
Abstract Highly ordered polycrystalline indium gallium oxide (PC‐IGO) film is obtained by the crystallization of room temperature sputtered amorphous IGO on a hot plate at 350 °C for 1 h and then annealed for 1 h in an N 2 O environment. A high‐density PC‐IGO of ≈7.15 g cm −3 with reduced oxygen vacancy (≈14.83%) and hydroxyl (OH) related defects (≈10.96%) has been obtained by N 2 O annealing. Self‐aligned coplanar thin‐film transistor (TFT) with the PC‐IGO exhibits the average saturation mobility of 78.73 cm 2 V −1 s −1 , threshold voltage of −1.07 V, subthreshold swing of 0.147 V dec −1 , and the on/off current ratio of over 10 8 . The TFTs show excellent stability under bias‐temperature stress with a negligible threshold voltage shift (Δ V TH ) of + 0.1 and −0.1 V for the positive and negative bias stresses, respectively. The TFTs exhibit very stable environmental stability when the TFTs are stored under high humidity (85%) and a high temperature (85 °C) for 2 days. The ring oscillator and the gate driver mode of the PC‐IGO TFTs exhibit the propagation delay of 7.44 ns/stage with rising/falling times of less than 0.7 μs, respectively. Therefore, the PC‐IGO TFTs are suitable for large area, high‐resolution active‐matrix organic, and inorganic light‐emitting diodes displays.