[9a-Z20-1~11] 21.1 Joint Session K "Wide bandgap oxide semiconductor materials and devices"

▼ [9a-Z20-6] Electric Field Thermopower Modulation Analyses of the Channel Thickness for SnO₂ Thin Film Transistors

〇(D)Doudou Liang^1,2, Binjie Chen³, Hai Jun Cho¹, Hiromichi Ohta¹ (1.RIES-Hokkaido Univ., 2.USTB, 3.IST-Hokkaido Univ.)

Keywords:Transparent thin film transistor, Amorphous SnO2, Electric field thermopower modulation

Recently, we clarified the operation mechanism of a-SnO₂ TTFT by field thermopower modulation analyses. The result showed that a 1.7 ± 0.4 nm-thick effective conducting channel formed at the interface between gate insulator and conducting channel with a 2.5-nm-thick depletion layer from the top surface in a 4.2-nm-thick bottom-gate top-contact type a-SnO₂ TTFT without any surface passivation. To further clarify the operating mechanism of a-SnO₂ TTFT, we measured the electric field modulated thermopower of the a-SnO₂ TTFTs with different thicknesses. The resultant a-SnO₂ TTFTs showed a decreased I_ON/I_OFF as increased the thickness of the SnO₂ conducting channel. The t_eff ≡ n_s/n_3D of the conducting a-SnO₂ channel increased with the thickness of the SnO₂ conducting channel. The 4.2 nm-thick SnO₂ TTFT shows the smallest t_eff with the best I_ON/I_OFF performance. From the thickness of the a-SnO₂ film and the t_eff, the carrier depletion depth at the top surface was concluded to be around 3−4 nm of the a-SnO₂ film, which shows a similar depletion length as reported data. The present results may provide the fundamental design concept of a-SnO₂ TTFT device.