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A comparison between cyclic out‐folding and in‐folding strain on flexible poly‐Si TFTs for foldable AMOLED display is reported. TFT under out‐folding stress exhibits severe degradation including positive threshold voltage (VTh) shift with unstable drain current (ID) than in‐folding, which is related to defect‐generation at poly‐Si grain‐boundary and justified using TCAD simulation. Stable low leakage current (<1 pA) after 30,000 mechanical folding cycles confirms the defect formation within poly‐Si and grain boundary protrusions. Electrical performance recovery using vacuum annealing after folding stress verifies the origin of electrical degradation as metastable traps generation. [ABSTRACT FROM AUTHOR]

We report high voltage amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) using a drain offset structure. The a-IGZO TFT with drain offset length ($\text{L}_{ {\mathrm{off}}}$) = $2.5~ \boldsymbol {\mu }\text{m}$ exhibits a maximum operating voltage ($\text{V}_{DS,Max}$) over 90 V, which increases with $\text{L}_{ {\mathrm{off}}}$. The drastic current drop from output characteristics appears for ${\text{V}}_{DS} > \text{V}_{DS, Max}$ with a positive threshold voltage shift and increased subthreshold swing from transfer characteristics. We obtain maximum lattice temperatures of \sim 130 °C for both the conventional and drain offset TFTs due to Joule heating (JH) within the a-IGZO layer by TCAD simulation. It indicates that the rise in temperature by JH is almost independent of $\text{L}_{ {\mathrm{off}}}$. The JH is uniformly distributed over the entire $\text{L}_{ {\mathrm{off}}}$ in drain offset TFT compared with a drastic increase near the drain side in conventional TFT. NF3 plasma treatment enhances conductivity at offset region, resulting in large $\text{V}_{DS, Max}$. [ABSTRACT FROM AUTHOR]

An amorphous indium gallium zinc oxide (a‐IGZO) layer is deposited on very thin conductive amorphous indium zinc oxide (a‐IZO) thin film to demonstrate high‐performance, coplanar thin‐film transistors (TFTs) with dual‐channel oxide semiconductor architecture. Based on material properties, a conduction band offset (∆EC) of ≈0.28 eV between a‐IZO and a‐IGZO layers and a conduction band bending of ≈0.3 eV at a‐IGZO/gate insulator (GI) interface exist. Through the electrical characterization, high field‐effect mobility (μFE) of ≈50 cm2 V−1 s−1, a positive threshold voltage (VTh) of ≈2.3 V, and low off‐current (IOFF) of <1 pA in coplanar a‐IZO/a‐IGZO TFT are demonstrated. The electron accumulation (>5 × 1018 cm−3) at both the a‐IZO/a‐IGZO and a‐IGZO/GI interfaces confirm the dual‐channel conduction. The bottom a‐IZO channel significantly contributes to increasing drain current (ID) due to large electron density (≈1019 cm−3). The dual‐channel coplanar TFT with a‐IGZO/IZO provides a guideline for overcoming the trade‐off between high μFE and positive VTh control for stable enhancement mode operation with increased ID. [ABSTRACT FROM AUTHOR]

We report the effect of N2O post-fabrication annealing (PFA) on the electrical stability of dual gate, active split amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT). Optimized N2O PFA at 360 °C for 3 h results in threshold voltage (VTH) close to zero and an increase in the on-current almost 2 times than as-fabricated TFT. N2O annealed TFT exhibited robust VTH stability under positive bias temperature stress at 60 °C and negative bias illumination stress, exhibiting $\Delta \text{V}_{\text {TH}}$ of 0.1 V, and- 0.1 V, respectively, whereas as-fabricated TFT showed large $\Delta \text{V}_{\text {TH}}$ of ~ 10 V and −3 V. The X-ray photoelectron spectroscopy depth profile reveals the origin of such improvement as the increasing metal-oxide bonds and the reduction in oxygen vacancy / OH related defects. [ABSTRACT FROM AUTHOR]

We report the effect of zinc-tin-oxide (ZTO) by spray coating on indium gallium zinc oxide (IGZO) thin-film transistor (TFT) for the improvement of both stability and performance. The IGZO/ZTO TFT exhibits the field effect mobility (${\mu }_{\text{FE}}$) of $18.39~{\text{cm}}^{2}{/\text{V}\cdot \text{s}}$ , threshold voltage ($\text{V}_{\text{Th}}$) of 0.1 V, and subthreshold swing (SS) of 0.16V/dec. The TFT shows excellent stabilities: $\Delta ~\text{V}_{\text{Th}}$ of −1.0 V for negative bias illumination stress (NBIS) and 0.4 V for hot carrier stress. These excellent performance and stability are correlated with the built-in electric field by charge distribution at the IGZO/ZTO hetero-junction. Therefore, ZTO spray coating on IGZO semiconductor can be a good technique to improve device stability. [ABSTRACT FROM AUTHOR]

We report a highly stable, nanocrystalline, zinc oxide (ZnO) thin-film transistor (TFT) fabricated by spray pyrolysis using purified ZrOx as a gate insulator. The crystalline ZnO layer shows an average grain size of 30 nm and a smooth surface with an average rms roughness value of 1.21 nm. The smoothness of the ZnO film is due to the alignment of all grains with the (002) c-axis. The TFTs exhibit a saturation mobility of 12.76 cm2 V ⋅ s, a subthreshold swing of 260 mV/dec, and an ON/OFF current ratio of ~108 with negligible hysteresis voltage. The ZnO TFT shows excellent stability under bias stress because of the high-quality ZnO film and its excellent interface with ZrOx. The conduction band tail width of ZnO was obtained from the TCAD fitting to the measurement data and was found to be 65 meV. [ABSTRACT FROM AUTHOR]

[Display omitted] • Combine effect of NH 3 and NF 3 plasma treatments on spray coated ZnO is studied by analyzing Hall Effect, UV-Vis, PL , AFM , XRD , XPS and SIMS. • It is concluded that NH 3 plasma contributes to control V th by forming V o -H complex and N incorporation and that NF 3 plasma improves the mobility and stability of ZnO TFT. We investigate the effects of NH 3 and NF 3 post plasma-treatment on the performance of spray-coated ZnO thin film transistors (TFTs). Both NH 3 and NF 3 plasma treatment are varied from 10 to 40 s. The properties of plasma treated ZnO were studied by Hall Effect measurements, UV–visible spectroscopy, photoluminescence, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. NF 3 plasma treatment causes n-type doping and generates carriers by F incorporation. While, NH 3 plasma can cause not only n-type doping by Hydrogen incorporation but also creates acceptor-like states by the formation of V o –H complex and inducing Nitrogen in ZnO. Owing to the N incorporation, the threshold voltage can be controlled by NH 3 plasma treatment. The appropriate NH 3 and NF 3 plasma treatments for 10 s each greatly enhance the performance of ZnO TFTs, exhibiting the saturation mobility and subthreshold swing of 20.65 cm2 V−1 s−1 and 0.18 V dec–1, respectively. Therefore, it is concluded that NH 3 and NF 3 plasma-treatment can be a useful technique to enhance the device performance and to improve the stability of solution-processed metal-oxide TFTs. [ABSTRACT FROM AUTHOR]