[25p-E202-1~15] 21.1 Joint Session K "Wide bandgap oxide semiconductor materials and devices"

▼ [25p-E202-1] Off-current reduction of InSnZnO_x thin film transistors by Ga-addition

〇(D)Hui Yang^1,2, Xiqing Zhang¹ (1.Beijing Jiaotong Univ., 2.RIES-Hokkaido Univ.)

Keywords:transparent amorphous oxide semiconductor, thin film transistor, InSnZnO

Transparent amorphous oxide semiconductor (TAOS, a-InGaZnO₄ is the representative) based thin-film transistors (TFTs) have widely commercialized as the backplane of OLEDs and LCDs in recent years from the points TAOS-TFTs exhibit rather high field-effect mobility (μ_FE ~10 cm² V⁻¹ s⁻¹) as compared to that of a-Si TFTs (μ_FE ~0.5 cm² V⁻¹ s⁻¹). In order to improve the resolution of OLEDs and LCDs, TAOS-TFTs that exhibits higher μ_FE are required. Among many TAOSs, we focus on an amorphous In-Zn-Sn-O (a-IZTO) system as a promising active TFT material that can satisfy the increasing demands for future displays because a-IZTO-TFTs show higher μ_FE (~30 cm² V⁻¹ s⁻¹). However, a-IZTO TFTs are not stable due to that oxygen vacancies are easily formed. In order to overcome this issue, we added Ga to a-IZTO. Because the introduction of Ga improves the stability of the electrical properties of n-type TAOS. Further, strong Ga−O bonding suppresses oxygen vacancy formation. We fabricated the a-IZTO: Ga TFTs with the bottom-gate structure on SiO₂/Si substrates by RF magnetron sputtering. The off current of the a-IZTO: Ga-TFT is hundred fA range, which is more than two orders of magnitude smaller than that of a-IZTO-TFT. The a-IZTO: Ga-TFT showed excellent device performance: μ_SAT of 36 cm² V⁻¹ s⁻¹, V_TH of 1.0 V, subthreshold swing S.S. of 420 mV decade⁻¹, and on-to-off current ratio I_ON/I_OFF of 3.8 × 10⁹. These results reveal that Ga addition to the IZTO channel layer is effective to improve the transistor characteristics of a-IZTO-TFTs.