Improvement of device characteristics of transparent thin-film transistors by using GaTiZnO/InGaZnO4 composite-channel structure

In this study, two types of transparent thin-film transistors (TFTs) were fabricated that exhibited with distinct channel designs. The first TFT contained a traditional 50-nm-thick amorphous indium gallium zinc oxide (a-IGZO) layer, and the second contained a double channel composed of composite channel layers of 10/40-nm-thick Ga-doped TiZnO (GTZO)/a-IGZO. The GTZO exhibited a carrier concentration of 2.43 × 10²¹ cm^-3, and served as both a carrier supplement and passivation layer, reducing oxygen absorption and back-channel charge trapping in the double-layer channel TFT. The a-IGZO TFT exhibited a carrier mobility of 3.7 cm²/V-s, subthreshold swing (SS) of 0.34 V/decade, off current of 7.23 × 10^-11, threshold voltage (V_th) of 1.48, and on/off current ratio of 7.3 × 10⁵. The GTZO/IGZO TFTs demonstrated enhanced device characteristics, namely an improved mobility of 16.9 cm²/V-s, SS of 0.25 V/decade, off current of 3.74 × 10^-12, V_th of 2.23, and on/off current ratio of 2.3 × 10⁷. Thus, the fabricated GTZO/IGZO TFTs exhibited high carrier mobility levels and improved device operation characteristics.