Low operating voltage InGaZnO thin-film transistors based on Al2O3 high-k dielectrics fabricated using pulsed laser deposition

Low-voltage-driven amorphous indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs) with an Al2O3 dielectric were fabricated on a Si substrate by using pulsed laser deposition. Both Al2O3 and IGZO thin films are amorphous, and the thin films have very smooth surfaces. The Al2O3 gate dielectric exhibits a very low leakage current density of 1.3 x 10-8 A/cm2 at 5 V and a high capacitance density of 60.9 nF/cm2. The IGZO TFT with a structure of Ni/IGZO/Al2O3/Si exhibits high performance with a low threshold voltage of 1.18 V, a high field effect mobility of 20.25 cm2V-1s-1, an ultra small subthreshold swing of 87 mV/decade, and a high on/off current ratio of 3 x 107.