Effect of gate insulator thickness on device performance of InGaZnO thin-film transistors

Abstract Top-contact thin-film transistors (TFTs) are fabricated in this work using atomic layer deposition (ALD) Al 2 O 3 as the gate insulator and radio frequency sputtering InGaZnO (IGZO) as the channel layer so as to investigate the effect of Al 2 O 3 thickness on the performance of IGZO-TFTs. The results show that TFT with 100-nm-thick Al 2 O 3 (100 nm-Al 2 O 3 -TFT) exhibits the best electrical performance; specifically, field-effect mobility of 5 cm 2 /Vs, threshold voltage of 0.95 V, I on / I off ratio of 1.1×10 7 and sub-threshold swing of 0.3 V/dec. The 100 nm-Al 2 O 3 -TFT also shows a substantially smaller threshold voltage shift of 1.1 V after a 10 V gate voltage is applied for 1 h, while the values for TFTs with an Al 2 O 3 thickness of 220 and 280 nm are 1.84 and 2 V, respectively. The best performance of 100 nm-Al 2 O 3 -TFT can be attributed to the larger capacitance and the smaller amount of total trap centers possessed by a thinner insulator compared to the thicker ones.