Synergistic Approach to High-Performance Oxide Thin Film Transistors Using a Bilayer Channel Architecture

Abstract

We report here a bilayer metal oxide thin film transistor concept (bMO TFT) where the channel has the structure: dielectric/semiconducting indium oxide (In2O3) layer/semiconducting indium gallium oxide (IGO) layer. Both semiconducting layers are grown from solution via a low-temperature combustion process. The TFT mobilities of bottom-gate/top-contact bMO TFTs processed at T = 250 °C are ~5tmex larger (~2.6 cm(2)/(V s)) than those of single-layer IGO TFTs (~0.5 cm(2)/(V s)), reaching values comparable to single-layer combustion-processed In2O3 TFTs (~3.2 cm(2)/(V s)). More importantly, and unlike single-layer In2O3 TFTs, the threshold voltage of the bMO TFTs is ~0.0 V, and the current on/off ratio is significantly enhanced to ~1 × 10(8) (vs ~1 × 10(4) for In2O3). The microstructure and morphology of the In2O3/IGO bilayers are analyzed by X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy, revealing the polycrystalline nature of the In2O3 layer and the amorphous nature of the IGO layer. This work demonstrates that solution-processed metal oxides can be implemented in bilayer TFT architectures with significantly enhanced performance.

High Electron Mobility Thin‐Film Transistors Based on Solution‐Processed Semiconducting Metal Oxide Heterojunctions and Quasi‐Superlattices

“…In contrast to previously published studies in which bi‐layered metal oxide structures and transistor channels were formed using similar chemical elements,48, 49 in the present systems, the large difference in the Fermi energies (Δ E F ) between the ZnO and In 2 O 3 layers (≈300 meV) is expected to lead to electron transfer from ZnO to In 2 O 3 upon physical contact (Figure 4b). Since the available energy levels at the CBM in the ultrathin In 2 O 3 are quantized (Figure 2c), the transferred electrons may well be confined in a 2D potential well.…”

Highly Effective Field-Effect Mobility Amorphous InGaZnO TFT Mediated by Directional Silver Nanowire Arrays

“…Currently, the sputtered and sol-gel amorphous indium-gallium-zinc oxide (a-IGZO) TFTs have a typical effective mobility in the range of 10-40 cm 2 /Vs and 1-14 cm 2 /Vs, respectively. 3,[5][6][7][8] Together with a large energy bandgap (> 3eV) to enable the transparency property, AOS TFTs are promising for developing flexible and transparent electronic devices. [9][10][11] Current developments of AOS TFTs have been focused on increasing the effective mobility, i.e.…”

Inkjet-Printed Oxide Thin-Film Transistors Using Double-Active Layer Structure

“…The inkjet printing process can afford better contact properties and a higher on-tooff current ratio due to smaller parasitic current, even in doubleactive layer TFTs. Significantly improved electrical properties of inkjet-printed In2O3/ZTO TFTs were obtained: a mobility of 8.6 cm 2 V -1 s -1 and threshold voltage of 2.76 V, which are higher values compared to previous solution-processed double active layer TFTs [8][9][10]18]. Interestingly, the mobility decreased and the threshold voltages shifted positively in the double-active layer TFTs with increasing In mole ratio.…”

“…In the case of the spin-coated double-active layer, the same double-active layer revealed an amorphous structure. In general, the processing temperature of the spin-coated double-active layer was the same temperature for each layer [9][10][11]. On the other hand, in the case of In2O3, the crystallinity and charge carriers occurred with increasing processing temperature, losing semiconductivity, and resulting in conductive properties [16,17].…”

“…Recently, solution-processed double-active layer oxide TFTs, in which heterostructured channels, were reported to obtain improved electrical properties at relatively low processing temperatures. Xinge et al fabricated bilayer metal oxide TFTs using IGO/In2O3 channel layers by spin coating and exhibited a TFT mobility of 2.56 cm 2 /V s at 250 o C [9]. They reported a significantly enhanced threshold voltage and on-to-off current ratio over single-layer TFTs.…”