High Field-Effect Mobility Two-Channel InGaZnO Thin-Film Transistors for Low-Voltage Operation

In this study, two-channel thin-film transistors (TC TFTs) using sputtered-deposited amorphous indium-gallium-zinc oxide (a-IGZO) as a channel layer and atomic-layer-deposition Al2O3 as gate insulator (GI) are proposed for wearable and portable device application. Symmetric-TC (S-TC) TFT structure consisted of conventional bottom gate (BG) TFT stacked on top of top gate (TG) TFT. Asymmetric-TC (A-TC) TFT contained BG TFT with tandem structure on the TG TFT. It was shown that the TC TFTs exhibited excellent performance such as high field-effect mobility (mu FE) and (ON/OFF) current ratio (I-ON/OFF) at low voltages (<2 V). For instance, the S-TC TFTs gave mu(FE) of 19.67 cm(2)Vs and I/(ON/OFF) of 5.48 x 10(8). Furthermore, the A-TC TFTs with tandem structure yielded mu(FE) of 30.15 cm(2)/Vs, a small threshold voltage of -1.25, a low subthreshold swing of 89 mV/decade, and a high knoFF of 1.70 x 10(9). It was found that the TC TFTs demonstrated better electrical performance than the sum of individual TG and BG TFTs. Under bias stress tests, the TC TFTs experience less V-th shift (Delta V-th) than the TG and BG TFTs.