In this study, InGaSnO (IGTO)-based bilayer In2O3/IGTO and IGTO/In2O3 thin-film transistors (TFTs) were designed, and their carrier transport mechanisms and electrical performances were investigated. Herein, the ultrathin In2O3 layer provided a higher carrier concentration (Ne), thus accumulating free carriers and enhancing the carrier mobility. The thick amorphous IGTO layer controlled the device and carrier conductance, yielding a reasonable threshold voltage (Vth). Consequently, the optimized bilayer In2O3/IGTO TFTs exhibited high field-effect mobility (μFE) of 43.6 cm2 V−1s−1 and good control with Vth of 1.2 V compared to the single layer In2O3 and IGTO TFTs. Experimental analysis indicated a decrease in the oxygen vacancy (VO) formation energy owing to the interaction between interstitial Ini and Sn. Consequently, numerous unpaired electrons were generated from VO at the hetero-interfaces. In addition, an analysis of the energy band shift indicated that the heterojunction generated parasitic channels to control the Ne, and the In2O3/IGTO TFT exhibited a smaller Rc (0.34 KΩ μm), which enhanced the μFE of TFTs. Overall, the high-performance bilayer In2O3/IGTO TFTs fabricated herein have significant potential for applications in thin-film electronics.

In this study, the effects of doping with different contents of the rare-earth element yttrium (Y) on the electrical performance of indium zinc oxide (IZO) and bilayer IZO/IYZO thin-film transistors (TFTs) were investigated. Through a rational design, the bilayer IZO/IYZO TFT exhibits the best performance with a Vth of 0.2 V and μFE of 32.6 cm2/V s. X-ray photoelectron spectroscopy band structure analysis demonstrated that, in the IZO/IYZO TFT, a 6-nm highly conductive ultrathin IZO provided free electrons and electron transfer from the IZO layer to the IYZO layer with the formation of band bending, thus increased the carrier mobility of devices. In addition, the 20-nm-thick IYZO layer controlled Ne and Vth by forming a potential barrier (0.38 eV), thereby increasing stability. Moreover, the experimental characterization revealed that Y doping can reduce the carrier concentration, oxygen vacancies, surface defects, and other trap densities of devices. Therefore, the IZO/IYZO TFT demonstrated the best stability with small Vth shifts of −0.9, 0.8, −1.1, and 1.0 V under negative gate bias stress, positive gate bias stress, negative gate bias light illumination stress, and positive gate bias light illumination stress measurements. Overall, the designed IZO/IYZO TFTs open effective pathways for achieving high-performance oxide TFTs.

This work investigates the effect of nitrogen and hydrogen (N/H) co-doping on the performance of ZnO thin-film transistors (TFTs). Optimum N/H co-doped ZnO TFTs showed high field-effect mobility (25.5 cm² Vs⁻¹) and I_on/I_off (10⁷) and low sub-threshold slope (0.25 V/dec.) and threshold voltage (1.2 V). X-ray photo-electron spectroscopy (XPS) and low-frequency noise analysis suggest that the observed improved electrical performance may be attributed to the reduction of the defect concentration and the average interface trap density due to the occupation of the N_O–H complex on the oxygen vacancy and Zn interstitials. Moreover, density functional theory calculation and XPS band structure results demonstrate that the N/H co-doped ZnO film slightly changed the valence band maximum energy offset, indicating that the N/H co-doping controlled the carrier concentration of the ZnO film due to the formation of neutral complex N–H states. The enhanced electrical performance of the N/H co-doped ZnO TFT shows significant potential for the use of low-cost thin film electronic applications.

In this study, hafnium (Hf) was doped into InZnO films and related thin-film transistors (TFTs) were fabricated using co-sputtering. The optimal concentration of Hf doping atoms was obtained by controlling the power of dual targets InZnO and HfO2 and comparing their performances with those of HfInZnO TFTs that were fabricated from a single target, thus achieving high-performance and highly stable HfInZnO TFTs. After optimization, high-performance HfInZnO (PIZO70W-PHfO250W) TFTs with μFE value of 26.1 cm2/V s, SS value of 0.251 V/dec., and Vth value of 0.7 V were obtained. The results of experimental characterization indicate that co-sputtering with Hf doping reduced the oxygen vacancies, surface defects, and other trap densities of the device. Moreover, the co-sputtering prepared HfInZnO TFT exhibited the highest stability for small Vth shifts of 0.8 (−0.9) and 1.2 (−1.6) V under the gate bias and light illumination stress tests. Furthermore, low-frequency noise measurements demonstrated that the optimal Hf doping concentration in the HfInZnO films was controlled by the dual-target co-sputtering method, resulting in a lower number of oxygen vacancies and a lower interface trap density of the devices, thus enhancing the stability of HfInZnO TFTs. Overall, HfInZnO TFTs prepared using dual-target co-sputtering are found to be useful for achieving high-performance oxide TFTs.

This study investigates the effect of aluminum (Al) content on the electrical performance and low-frequency noise (LFN) characteristics of InAlZnO (IAZO) thin-film transistors (TFTs). Furthermore, the IAZO TFTs with Al content of 0.5 at. % exhibit a desirable device performance, which includes the field-effect mobility (µFE) of 14.1 cm2/V s, a subthreshold swing of 270 mV·dec−1, and threshold voltage (VTH) of 0.1 V. Based on the x-ray photoelectron spectroscopy band structure, photoluminescence, electron paramagnetic resonance, spectroscopic ellipsometry donor state analysis, and LFNs characterizations, the improvement in electrical properties of IAZO TFTs is attributed to the appropriate Al content (0.5 at. %) within the IAZO film. This optimal Al incorporation not only controls the carrier concentration and shallow donor state but also suppresses the oxygen-vacancy (VO) defects and passivates the trap density at the SiO2/IAZO interfaces. Moreover, the LFN measurements revealed a 1/f noise dominance of the carrier number fluctuation (ΔN) model. It can be indicated carrier trapping and release by trap states within the SiO2/IAZO interface. This work provides a precise and efficient method to evaluate the quality of the interface in IAZO TFTs.

In this work, the hydrogenation (H) of Mg-doped amorphous InGaZnO (a-IGZO:Mg/H) thin-film transistors (TFTs) was fabricated via RF sputtering method. As a consequence, the a- IGZO:Mg/H TFT with field-effectmobility of 35.6 cm ² /Vs, lowsub-threshold swing of 0.21 V/dec, high I _on /I _off of 10 ⁸ , andsmall threshold voltage ( V _th ) of 0.5 V was obtained. In addition, the a- IGZO:Mg/H TFT exhibits the best stability for small V _th shifts of 1.5 (-1.7) V, 2.6 (-2.8) V, and 3.5 (-3.6) V under the conditions of gate bias, light illumination, and the temperature stress test. The X-ray photo-electron spectroscopy band structure and oxygen vacancy ( V _O ) analysis indicate that the enhanced performance and stability are owing to the appropriate Mg/H co-doping concentration. This is because the Mg/H co-doped not only controlled the carrier concentration, but also reduced V _O and interface trap density. Overall, the optimized Mg/H co-doped a-IGZO TFTs have provided an effective pathway to achieve high-performance oxide TFTs with superior stability.