Theoretical assessment of multi-doping strategies in amorphous indium oxide for synergistically enhancing carrier mobility and bias stability

Abstract

Amorphous indium oxide (a-In₂O₃) materials treated with various dopants are leading candidates for advanced display technologies. As the channel layer in thin-film transistors (TFTs), the material must simultaneously exhibit high carrier mobility and robust bias stability. However, current experimental results predominantly reveal an empirical trade-off between these two parameters, which poses significant challenges for rational material design. In this work, we carried out a density functional theory (DFT) study, assisted by ab initio molecular dynamics (AIMD) simulations, to theoretically assess multi-doping strategies in the a-In₂O₃ system. The effect of foreign metal dopants, including zinc (Zn), cadmium (Cd), gallium (Ga), tin (Sn), praseodymium (Pr), and tungsten (W), on the mobility and bias stability of the host material was evaluated by the extracted effective electron mass and metal–oxygen bond length, respectively. Our results show that, compared to the conventional quaternary indium–gallium–zinc–oxide (IGZO) system, the pentanary indium–tin–gallium–zinc–oxide (ITGZO) design could concurrently enhance the carrier mobility and bias stability of the film. The simulation results are in agreement with the reported experimental findings. Such a theoretical assessment approach may pave the pathway to source material design of novel metal oxide semiconductor materials.

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1. Introduction

Thin-film transistor (TFT) technology has revolutionized the display industry, enabling the transition from cathode-ray tube (CRT) technology to advanced systems—such as liquid crystal displays (LCDs) and organic light-emitting diode (OLED) displays.^1–5 The continuing advancement of display technologies towards large-area formats, ultra-high resolution (8 K/16 K), flexible/foldable architectures, and ultra-low power consumption has resulted in higher performance requirements for TFT devices. Current critical challenges primarily involve the synergistic enhancement of high field-effect mobility (>50 cm² V⁻¹ s⁻¹), environmental stability, low-cost fabrication, and mechanical flexibility.^6–10

Among existing TFT technologies, amorphous silicon (a-Si) faces inherent limitations in mobility (approximately 1 cm² V⁻¹ s⁻¹), which limits its applicability in high-refresh-rate displays and high-density pixel integration.¹¹ Although low-temperature polycrystalline silicon (LTPS) exhibits higher mobility (50–100 cm² V⁻¹ s⁻¹), its complex photolithography and annealing procedures restrict its utility for large-area panels while also increasing production costs.¹² In this context, metal oxide semiconductor (MOS)-based TFTs facilitate promising solutions to overcome these technical barriers, leveraging their unique amorphous structure, wide-bandgap characteristics, and compatibility with low-temperature processing.^13–15

Indium–gallium–zinc oxide (IGZO)-based MOS-TFTs have achieved commercial success, demonstrating field-effect mobility (approximately 10 cm² V⁻¹ s⁻¹) that is 1–2 orders of magnitude higher than that of a-Si, coupled with ultra-low leakage current (<1 × 10⁻²² A µm⁻¹) and excellent optical transparency.^16–18 However, conventional IGZO materials encounter substantial limitations in carrier mobility and operational stability when applied to next-generation ultra-high-frame-rate displays (>240 Hz), dynamic random-access memory (DRAM) architectures demanding rapid read/write operations, and flexible wearable electronics.^19,20

To address these challenges, researchers have systematically explored different doping strategies in amorphous indium oxide systems to investigate the feasibility of concurrently achieving high carrier mobility and device stability.^21–25 Nevertheless, the mechanistic understanding and theoretical framework remain elusive, obscuring the design principles for next-generation material development.

In this work, we determined the amorphous structure of multicomponent (Zn, Cd, Ga, Pr, Sn, W) oxide systems via ab initio molecular dynamics (AIMD) simulations. Density functional theory (DFT) has been widely used for accurate calculations of electronic structure properties,^26–30 and we performed DFT calculations based on the obtained amorphous structures. This research establishes its novelty by building a direct theoretical link through two key parameters, namely the effective electron mass and metal–oxygen bond length, to connect them with critical TFT performance metrics, including carrier mobility and bias stability. Based on such a theoretical assessment approach, we demonstrate some guiding principles for designing new MOS materials for use in advanced TFT applications.

2. Methodology

Amorphous systems were constructed using a melt-quenching-based AIMD simulation, which has been extensively validated for structural studies of amorphous materials^31–33 (see the flowchart in Fig. 1). Initially, canonical (NVT) ensemble AIMD simulations were performed with a 2-fs time step and melting at 3000 K for 10 ps to eliminate crystalline symmetry. Subsequently, the system was cooled to 200 K at a rate of 0.2 K fs⁻¹. To overcome the limitations of using atoms from a single unit cell to represent the amorphous structure, the structures were further equilibrated for an additional 5000 MD steps at 300 K, and structural properties (e.g., bond length distributions) were analyzed as time-averaged quantities.

Fig. 1 Flow chart of the melt-quenching step to obtain an amorphous structure (a-In₂O₃).

Finally, six geometric configurations were randomly chosen from the equilibrium phase of the room-temperature MD simulation. These configurations were subsequently subjected to structural optimization to obtain their electronic band structures. All MD steps were performed using a plane-wave cutoff energy of 520 eV, with Brillouin zone sampling restricted to the Γ-point only, and the energy convergence criterion was set to 1 × 10⁻⁶ eV per step.

A systematic multi-element doping modeling strategy was developed to optimize oxide semiconductor systems, initiated from an 80-atom bixbyite-type In₂O₃ supercell containing 32 In and 48 O atoms. The lattice constants of this supercell were fully optimized, resulting in a cubic cell with a = b = c = 10.18 Å. It was demonstrated that this supercell is sufficient for modeling amorphous characteristics,^34,35 with an initial density of 6.845 g cm⁻³.

This strategy proceeded through three progressive stages: (1) strategically incorporating Zn into the In–O system to form an In–Zn–O (IZO) ternary amorphous network, with a precisely controlled Zn/(In + Zn) atomic ratio (18.8%, 37.5%, 50.0%, i.e., IZO6, IZO12, IZO16, respectively) to establish a compositional gradient model; (2) incorporating Ga, Cd, Sn, W, and Pr into the IZO system (i.e., IGZO, ICZO, ITZO, IWZO, and IPZO, respectively) to construct quaternary composite systems, where each dopant was introduced at a concentration of 3.1% via substitution of one In atom; (3) engineering a Ga/Sn co-doped IZO (ITGZO) penternary architecture through synergistic doping strategies, with Ga and Sn doping concentrations set at 3.1%.

All doped structures were constructed to ensure charge neutrality within the supercell. To ensure charge neutrality within the supercell, charge compensation was achieved through the introduction of oxygen vacancies, electrons, or holes. Detailed structural information for the supercell is provided in Table S1. The radial distribution function (RDF) plots for each system are presented in Fig. S1.

All calculations were performed using the Vienna Ab initio Simulation Package (VASP), with plane-wave basis sets for valence electron representation, and the projector augmented wave (PAW) method for electron–ion interactions. The Perdew–Burke–Ernzerhof generalized gradient approximation (GGA-PBE) was selected for the exchange–correlation functional, with the cutoff energy set to 520 eV, and the k-point mesh was adopted in a 3 × 3 × 3 gamma-centered scheme. The energy convergence criterion was defined as 1 × 10⁻⁶ eV per iteration step, with atomic forces constrained to below 0.02 eV Å⁻¹ as the force convergence criterion. The electronic band structure was interpolated along the path X → Γ → Y → Γ → Z, with 20 k-points uniformly sampled between each pair of high-symmetry points. Amorphous structures were visualized with the VESTA program,³⁶ while electronic band structures and density-of-states diagrams were derived through VASPKIT post-processing,³⁷ in which the Fermi level (E_F) was set to zero by default.

We evaluated electron mobility and bias stability of the amorphous system in terms of two key parameters: the effective electron mass and the M–O bond length (M is a foreign metal). The electron mobility, denoted by µ_e, is expressed in equation form as follows:

where e denotes the electron charge, denotes the effective electron mass, and τ denotes the mean free time. As demonstrated in eqn (1), the effective electron mass is a crucial factor in determining the ease with which high mobility can be achieved. The smaller the effective electron mass, the easier it is to obtain high mobility. The effective electron mass can be derived by fitting the parabolic conduction band minimum (CBM) by:where ε(k), ħ, and k represent the band dispersion relation, the reduced Planck constant, and a wave vector, respectively.

In amorphous oxides, oxygen vacancies (V_O) typically act as deep donor defects, leading to significant threshold voltage shifts (ΔV_th), particularly under negative bias stress (NBS) and negative bias illumination stress (NBIS) conditions.^38,39 Therefore, the concentration of V_O in the MOS directly affects the stability of the TFT device.⁴⁰ The effect of doping elements on the stability of the TFT device can be demonstrated by determining whether they inhibit the V_O concentration.

It is worth noting that while the oxygen vacancy formation energy is a common indicator, it was not adopted here because its value can significantly vary between oxygen sites in an amorphous structure due to the lack of periodicity. The binding energy between the foreign metal M and oxygen exhibits a positive correlation with the efficacy of V_O inhibition,^21,41 where a decrease in bond length corresponds to an increase in binding energy and enhanced V_O suppression.⁴²

3. Results and discussion

3.1. Doping effect of zinc on the amorphous In₂O₃ host matrix

Fig. 2(a) shows a plot of effective electronic mass versus zinc doping ratio in the amorphous IZO (a-IZO) system. We note that all effective electron mass values were derived from calculations of the curvature of the CBM, and corresponding pseudo-band structures are provided in Fig. S2. In₂O₃ is a typical n-type wide-bandgap semiconductor that exhibits a low effective electron mass (0.180m₀, where m₀ denotes the rest mass of an electron), even in its amorphous state. This phenomenon can be attributed to the predominance of the In 5s orbitals in the CBM, which exhibit spherically distributed electronic states.¹⁶ Consequently, the CBM characteristics remain largely insensitive to the degree of atomic disorder, thereby preserving the low effective electron mass characteristic of crystalline In₂O₃.

Fig. 2 (a) Effective electron mass of IZO with different Zn-doping concentrations. (b) Crystal structure of IZO 18.8% (In shaded in purple, Zn shaded in grey). The density-of-states plots (CBM region, E_F = 0 eV) for Zn-doping concentrations of (c) 18.8%, (d) 37.5%, and (e) 50%.

These properties suggest the great potential for achieving high carrier mobility in a-In₂O₃. However, metal oxide thin films with high mobility frequently exhibit excessive oxygen vacancy defects, which elevate carrier concentrations above critical thresholds and induce significant negative threshold voltage shifts. These effects have been shown to severely compromise gate electric-field modulation of source-drain current, thereby degrading the TFT switching performance and operational stability.^41,43

The Zn–O bond length of 2.04 Å is shorter than the In–O bond length of 2.21 Å (Fig. S3(a)). This stronger and shorter bonding helps suppress the formation of V_O, thereby reducing the carrier concentration. The experimental results show that the doping of In₂O₃ with Zn can effectively suppress excessive carrier concentration.^44,45 As the Zn-doping concentration increases, the effective electron mass exhibits a corresponding enhancement, increasing from 0.180m₀ for intrinsic indium oxide to 0.188m₀ at 18.8% doping, and further to 0.195m₀ at 37.5% doping. When the doping concentration reaches 50%, the effective electron mass attains its maximum value of 0.207m₀, consistent with the experimentally observed positive correlation between indium content and carrier mobility.^46,47

Fig. 2(c)–(e) depict the density of states (DOS) at the conduction band minimum for IZO6, IZO12, and IZO16, respectively. In all DOS plots, the Fermi level is set as the zero of energy. Based on the DOS analysis, the increase in effective electron mass can be attributed to the perturbation of the conduction band minimum induced by the foreign orbitals introduced by Zn doping. A higher doping concentration leads to a stronger perturbation, which consequently results in a gradual increase in the effective electron mass.

Considering the sensitivity of ZnO components to moisture and temperature,^48,49 which may trigger compositional segregation and structural degradation, we adopted Zn-doped systems with a lower Zn content (18.8 at%) to balance the material stability and electrical performance. Nevertheless, Zn incorporation remains essential due to the tendency of Zn²⁺ to form an energy-stable [ZnO₄] tetrahedral coordination structure (as shown in Fig. 2(b)), which is conducive to the maintenance of the amorphous structure of IGZO^50,51 and is necessary for the preparation of large-area uniform films and flexible devices.

3.2. Exotic metal doping effects in the a-IZO system

From an electronic structure perspective, In³⁺ (with principal quantum number n = 5) displays an outer electron configuration of 4d¹⁰5s⁰. In comparison to the 3d¹⁰4s⁰ configuration of Zn²⁺, the 5s orbital radius of the former (In³⁺ 5s) is significantly larger than the 4s orbital radius of the latter. When the two types of s-orbitals overlap, a larger orbital radius results in a more substantial orbital overlap volume, thereby markedly enhancing the electron transport efficiency. To investigate the influence of foreign s-orbitals on the electron transport performance, we selected five doping elements with specific s-orbital configurations: Ga (4s orbital), Sn/Cd (5s orbital), and W/Pr (6s orbital). The impact of foreign metal (M) doping on MOS stability was also investigated.

It has been established through previous studies that oxygen vacancies are the main source of free carriers in a-IZO systems.⁵²Fig. 3(a) illustrates the M–O bond lengths after doping with foreign metals M (see Fig. S3 for the distribution of M–O bond lengths). Table S2 compiles the experimental measurements and theoretical predictions of M–O bond lengths in IGZO, which exhibit a strong concurrence with the calculations presented in this work. Bond length analysis in the metal-doped systems revealed significant contractions in the Ga–O (1.90 Å) and W–O (1.95 Å) bonds compared to the In–O (2.21 Å) and Zn–O (2.04 Å) bonds, indicating that the high binding energies of the Ga–O and W–O bonds effectively suppressed V_O formation, which is consistent with the experimental results.^21,53

Fig. 3 (a) M–O bond length and (b) effective electron mass of a-IMZO. (c) ITZO and (d) ICZO density-of-states plots (CBM region, E_F = 0 eV).

This observation provides atomic-scale insights into the structural origin of the enhanced stability of Ga-doped IGZO-based TFT devices. The calculated effective electronic mass in Fig. 3(b) demonstrates that dopants with 5s orbital characteristics, such as Sn⁴⁺ (0.180m₀) and Cd²⁺ (0.189m₀), lead to a reduced or nearly unchanged effective mass relative to a-IZO (0.188m₀). This confirms that the strong overlap of the electron cloud between the 5s orbitals significantly enhances the carrier transport properties. The contributions of Sn- and Cd-doped 5s orbitals to the CBM are further detailed in Fig. 3(c) and (d).

Notably, while Sn- and Cd-doped IZO systems display excellent high-mobility potential, the averaged Sn–O (2.10 Å) and Cd–O (2.31 Å) bonds lengths do not tend to decrease compared to In–O (2.21 Å) and Zn–O (2.04 Å) bonds, which mechanistically suggests the absence of inhibitory effects on V_O formation. In contrast, Ga/W-doped systems effectively inhibit the formation of V_O; however, obtaining high mobility remains challenging. This inverse correlation between the performance parameters reveals an inherent trade-off between carrier mobility and structural stability in metal oxide semiconductors.

3.3. Synergistic enhancement of carrier mobility and bias stability in a Sn/Ga co-doped a-IZO matrix

In this study, we built upon the foundations laid by quaternary systems, strategically incorporating Ga (stability-friendly) and Sn (mobility-friendly) with In, Zn, and O to form a pentanary compound. Fig. 4(a) shows the M–O bond lengths and effective electron mass of ITGZO, and Fig. 4(b) presents its DOS plots. The DOS analysis revealed that the CBM of ITGZO retained the characteristic features of ITZO, with the In 5s orbitals remaining dominant and Sn doping introducing additional 5s orbital contributions to the CBM, thus ensuring efficient electron transport pathways. The calculated effective electronic mass of 0.181m₀ was nearly identical to that of high-mobility ITZO (0.180m₀) and substantially lower than that of IGZO (0.223m₀), demonstrating the superior high-mobility potential of ITGZO.

Fig. 4 (a) Plot of M–O bond length and effective electron mass variation of ITGZO compared to IGZO and ITZO. (b) Density of states plot (CBM region, E_F = 0 eV) of ITGZO.

The Ga–O bond length (1.898 Å) and the Sn–O bond length (2.089 Å) closely match the corresponding bond lengths in IGZO (1.904 Å) and ITZO (2.098 Å), respectively. This agreement indicates that ITGZO retains the ability of Ga³⁺ to suppress oxygen vacancies and the characteristic of Sn⁴⁺ to maintain a low effective electron mass. Consequently, while preserving the high carrier mobility of ITZO, ITGZO is expected to more effectively inhibit the formation of oxygen vacancies, with a consequent improvement in bias-stress stability.

The computational data presented herein demonstrated that ITGZO attained the synergistic effect of electron transport path optimization and oxygen vacancy defect suppression on a microscopic scale through the Ga/Sn dual-site doping mechanism. In recent years, there has been an increased focus on the study of ITGZO as a potential replacement for IGZO. Table 1 summarizes the relevant experimental data regarding the mobility and negative bias illumination stress (NBIS) stability, which is typically characterized by the threshold voltage shift (ΔV_th), for ITGZO and IGZO.

Table 1 Mobility and NB(I)S of ITGZO and IGZO in experiments

ITGZO		IGZO
μ/cm^2 V^−1 s^−1	NB(I)S/ΔVth/V	μ/cm^2 V^−1 s^−1	NB(I)S/ΔVth/V	Year	Ref.
30.6	∼0	—	—	2019	59
65	—	4.3	—	2021	60
11.5	−0.1	6	−0.9	2023	54
85.9	−0.16	19.1	−0.1	2022	55
46.7	−0.4	20.3	−0.4	2020	56
90.2	−0.08	—	—	2023	61

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It is noteworthy that the reported values in these studies^54–56 exhibit a certain degree of variability. This can primarily be attributed to differences in processing conditions, such as thin-film deposition methods, annealing temperatures, and layer thicknesses,⁵⁷ which significantly impact the crystallinity and defect density of the films, thereby influencing mobility. Furthermore, the mobility values themselves may differ depending on the measurement technique employed (e.g., Hall mobility versus field-effect mobility). Similarly, the magnitude of the NBIS-induced ΔV_th is highly dependent on specific testing parameters,⁵⁸ including applied bias voltage, illumination intensity, and stress duration.

Despite these variations, a consistent trend is evident from the compiled data: ITGZO demonstrates a significant enhancement in mobility relative to IGZO, while maintaining comparable NBIS stability. The agreement with the experimental results confirms the reliability and accuracy of our simulation work. Theoretical and experimental studies have confirmed that, as a thin-film transistor channel material, ITGZO demonstrated the potential to overcome the material design bottleneck of the mutual constraints of mobility and stability in traditional metal oxide semiconductors.

Our study reveals the synergistic optimization mechanism of ‘functional complementary doping’, which provides a new idea for the development of new MOS materials. By simultaneously introducing heterogeneous elements with stabilizing effects (e.g., Ga) and high-mobility properties (e.g., Sn), we have successfully broken through the mutual exclusion bottleneck of mobility-stability in the traditional single-doping system. This provides a paradigm for the development of multivariate MOS materials: (1) prioritizing the screening of element combinations with matching outer electronic orbitals (e.g., synergistic 5s orbitals of In with 5s orbitals of Sn/Cd) to maintain the maximal electron transport paths at the CBMs; and (2) directionally assigning the roles of different elements (e.g., Ga to suppress oxygen vacancies and Sn to optimize the carrier transport) to achieve synergistic enhancement of the material properties.

Additionally, this study provides a theoretical basis and data analysis framework for high-throughput computational screening of advanced MOS materials, which can quickly target high-potential doping combinations by establishing a multi-parameter evaluation matrix such as electronic density of states, effective electron mass, and metal–oxygen bond length. It should be noted that the present model, while effective within its defined scope, does not incorporate certain factors such as carrier scattering mechanisms or the influence of specific defects (e.g., hydrogen). Investigating these factors represents an important direction for future work and will contribute to further refining the theoretical framework.

4. Conclusions

We performed AIMD-assisted DFT simulations of ternary, quaternary, and penternary MOS materials within the a-In₂O₃ host structure. Dopants of Zn, Cd, Ga, Pr, Sn, and W were studied. The effective carrier mass and metal–oxygen bond length were determined to assess each doped configuration. In conventional quaternary MOS systems, such as IGZO and IWZO, the stronger bonding strength of Ga–O (1.904 Å) and W–O (1.949 Å) compared to In–O (2.211 Å) and Zn–O (2.037 Å) effectively suppressed oxygen vacancy formation, thereby enhancing bias stability. However, these systems exhibited relatively high effective electron mass (0.223m₀ and 0.212m₀, respectively). In contrast, ITZO and ICZO demonstrate reduced effective electron mass (0.180m₀ and 0.189m₀), yet their Sn–O (2.098 Å) and Cd–O (2.312 Å) bond lengths showed no significant reduction relative to In–O and Zn–O bonds, and failed to inhibit oxygen vacancy defects.

Furthermore, we demonstrated that the penternary ITGZO system effectively suppressed oxygen vacancies while maintaining a lower effective electron mass (0.181m₀). The experimental validation of our methodology (with established data) demonstrates its remarkable effectiveness, offering a promising paradigm for next-generation MOS material design.

Author contributions

Jiejun Pan, Pingqi Gao, and Can Han jointly conceived and designed the study. Jiejun Pan performed the DFT calculations and analysed the data. Pingqi Gao, Can Han, Zhibin Liu, Xionghui Tan, and Kaixuan Chen assisted with discussion. Jiejun Pan, Pingqi Gao, and Can Han wrote the manuscript. All authors contributed to the final version of this manuscript.

Conflicts of interest

There are no conflicts to declare.

Data availability

The authors confirm that the data supporting the findings of this study are available within the article. The raw data that support the findings of this study are available from the corresponding author, upon reasonable request.

Supplementary information (SI) is available. See DOI: https://doi.org/10.1039/d5cp02257f.

Acknowledgements

This work was financially supported by the National Key R&D Program of China (2023YFB4204600), the Shenzhen Science and Technology Program (KJZD20230923114412026, and KJZD20231023095959001), and the Yibin Science and Technology Program (2023JB007).

References

1. C. D. Sheraw, L. Zhou, J. R. Huang, D. J. Gundlach, T. N. Jackson, M. G. Kane, I. G. Hill, M. S. Hammond, J. Campi, B. K. Greening, J. Francl and J. West, Organic thin-film transistor-driven polymer-dispersed liquid crystal displays on flexible polymeric substrates, Appl. Phys. Lett., 2002, 80, 1088–1090.
2. J.-S. Park, T.-W. Kim, D. Stryakhilev, J.-S. Lee, S.-G. An, Y.-S. Pyo, D.-B. Lee, Y. G. Mo, D.-U. Jin and H. K. Chung, Flexible full color organic light-emitting diode display on polyimide plastic substrate driven by amorphous indium gallium zinc oxide thin-film transistors, Appl. Phys. Lett., 2009, 95, 013503.
3. J. Shi, J. Zhang, L. Yang, M. Qu, D.-C. Qi and K. H. L. Zhang, Wide Bandgap Oxide Semiconductors: from Materials Physics to Optoelectronic Devices, Adv. Mater., 2021, 33, 2006230.
4. W.-B. Jeong, S.-H. Kim, H.-J. Chung and S.-W. Lee, IR drop-independent 8T1C LTPS pixel circuit for medium-sized AMOLED displays, J. Inf. Display, 2025, 1–12.
5. Y. Long and H. Meng, Key components for active-matrix OLED displays: Fundamentals and market status, J. Lumin., 2025, 280, 121099.
6. D. Wang, M. Furuta, S. Tomai and K. Yano, Understanding the Role of Temperature and Drain Current Stress in InSnZnO TFTs with Various Active Layer Thicknesses, Nanomaterials, 2020, 10, 617.
7. T. Kamiya, K. Nomura and H. Hosono, Present status of amorphous In–Ga–Zn–O thin-film transistors, Sci. Technol. Adv. Mater., 2010, 11, 044305.
8. C. Li, X. Lin, P. Hu, B. Hu, J. Wang, W. Wang, X. Xu, X. Fang, R. Zhou, Y. Liao, S. Lee, B. Wang, L. Lin and S. Park, 56-4: Exploration of Ultra-Large Size 16K High Resolution Technology, SID Symposium Digest of Technical Papers, 2023, 54, 811–813.
9. J. Wu, M. Guo, Q. Wu, S. Han, X. Lu, X. Liang and C. Liu, Achieving high mobility and enhanced illumination stability in InPrO homojunction thin-film transistors, Appl. Phys. Lett., 2025, 126, 093502.
10. Y. Zhang, B. Luo, J. Liu, B. Chen, X. Wu, X. Wu, R. Bai, D. W. Zhang, Q. Sun, S. Hu and L. Ji, Comprehensive Optimization Strategies for InSnZnO Grade-Channel Thin-Film Transistors via Atomic Layer Deposition, IEEE Trans. Electron Devices, 2025, 72, 1815–1821.
11. N. Lu, W. Jiang, Q. Wu, D. Geng, L. Li and M. Liu, A Review for Compact Model of Thin-Film Transistors (TFTs), Micromachines, 2018, 9, 599.
12. J. F. Wager, Flat-Panel-Display Backplanes: LTPS or IGZO for AMLCDs or AMOLED Displays?, Inf. Disp., 2014, 30, 26–29.
13. N. Tiwari, A. Nirmal, M. Rameshchandra Kulkarni, R. Abraham John and N. Mathews, Enabling high performance n-type metal oxide semiconductors at low temperatures for thin film transistors, Inorg. Chem. Front., 2020, 7, 1822–1844.
14. L. Zhang, H. Yu, W. Xiao, C. Liu, J. Chen, M. Guo, H. Gao, B. Liu and W. Wu, Strategies for Applications of Oxide-Based Thin Film Transistors, Electronics, 2022, 11, 960.
15. L. Petti, N. Münzenrieder, C. Vogt, H. Faber, L. Büthe, G. Cantarella, F. Bottacchi, T. D. Anthopoulos and G. Tröster, Metal oxide semiconductor thin-film transistors for flexible electronics, Appl. Phys. Rev., 2016, 3, 021303.
16. K. Nomura, H. Ohta, A. Takagi, T. Kamiya, M. Hirano and H. Hosono, Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors, Nature, 2004, 432, 488–492.
17. K. Abe, K. Takahashi, A. Sato, H. Kumomi, K. Nomura, T. Kamiya, J. Kanicki and H. Hosono, Amorphous In–Ga–Zn–O Dual-Gate TFTs: Current–Voltage Characteristics and Electrical Stress Instabilities, IEEE Trans. Electron. Devices, 2012, 59, 1928–1935.
18. H. Fujiwara, Y. Sato, N. Saito, T. Ueda and K. Ikeda, Surrounding Gate Vertical-Channel FET With a Gate Length of 40 nm Using BEOL-Compatible High-Thermal-Tolerance In-Al-Zn Oxide Channel, IEEE Trans. Electron. Devices, 2020, 67, 5329–5335.
19. L. Liang, H. Zhang, T. Li, W. Li, J. Gao, H. Zhang, M. Guo, S. Gao, Z. He, F. Liu, C. Ning, H. Cao, G. Yuan and C. Liu, Addressing the Conflict between Mobility and Stability in Oxide Thin-film Transistors, Adv. Sci., 2023, 10, 2300373.
20. H. Hosono, (Invited) Approach to Oxide Tfts with High Mobility & Stability, Meet. Abstr., 2022, MA2022-02, 1255.
21. D. Wan, X. Liu, A. Abliz, C. Liu, Y. Yang, W. Wu, G. Li, J. Li, H. Chen, T. Guo and L. Liao, Design of Highly Stable Tungsten-Doped IZO Thin-Film Transistors With Enhanced Performance, IEEE Trans. Electron Devices, 2018, 65, 1018–1022.
22. W.-Y. Lee, H. Lee, S. Ha, C. Lee, J.-H. Bae, I.-M. Kang, K. Kim and J. Jang, Effect of Mg Doping on the Electrical Performance of a Sol-Gel-Processed SnO₂ Thin-Film Transistor, Electronics, 2020, 9, 523.
23. W. Xu, C. Xu, Z. Zhang, W. Huang, Q. Lin, S. Zhuo, F. Xu, X. Liu, D. Zhu and C. Zhao, Water-Induced Nanometer-Thin Crystalline Indium-Praseodymium Oxide Channel Layers for Thin-Film Transistors, Nanomaterials, 2022, 12, 2880.
24. Y. Yang, H. Ning, D. Luo, Z. Xu, Z. Fang, W. Xu, Z. Zhang, B. Jiang, R. Yao and J. Peng, High transparent and stability indium praseodymium oxide thin-film transistors with tungsten doping by solution method, Surf. Interfaces, 2024, 44, 103704.
25. Y. Han, Y. Chen, M. Li, H. Xu, M. Xu, L. Wang and J. Peng, Abnormal Positive Shift of Threshold Voltage in Praseodymium-Doped InZnO-TFTs Under Negative Bias Illumination Temperature Stress, IEEE Trans. Electron Devices, 2024, 71, 1951–1956.
26. M. Zubair, A. Ullah, S. Belhachi, N. Rahman, M. Husain, K. M. Abualnaja, N. Sfina, M. Uzair, M. Asif, V. Tirth and M. I. Saleem, DFT Analysis of Sr₂GdMO₆ (M = Bi, Sb) Double Perovskites for Spintronics and UV Optoelectronics, J. Supercond. Novel Magn., 2025, 38, 169.
27. M. R. Pazuki, J. J. Sardroodi and S. Rastegar, A DFT study of the effect of strain on the structural and electronic properties of perovskite APbBr₃ (A = K, Rb, and Cs), Sci. Rep., 2025, 15, 26724.
28. S. Belhachi, S. Al-Qaisi, S. Samah, H. Rached, A. Zaman, T. A. Alrebdi, A. Boutramine, N. Erum, R. Ahmed and A. S. Verma, DFT Analysis of Ba₂NbRhO₆: A Promising Double Perovskite for Sustainable Energy Applications, J. Inorg. Organomet. Polym., 2025, 35, 978–993.
29. N. Rahman, K. M. Abualnaja, S. Belhachi, N. Sfina, M. Husain, B. M. Al-Khamiseh, A. Azzouz-Rached, H. A. Althobaiti, S. Ullah, R. Khan and M. Asghar, DFT Insights on the Future Prospects of Ba₂PrXO₆ (X  =  Ir, Pt) Double Perovskites for High-Energy Applications, J. Inorg. Organomet. Polym., 2025, 35, 1439–1452.
30. N. Sfina, N. Rahman, S. Belhachi, M. Husain, B. M. Al-Khamiseh, K. M. Abualnaja, G. Alosaimi, A. Azzouz-Rached, S. Ullah, A. U. Rashid and R. Khan, Exploring Novel Ba₂MBiO₆ (M  =  Sm, Tb) Oxide Double Perovskites Employing DFT, J. Inorg. Organomet. Polym., 2024, 34, 6102–6113.
31. J. Kang, X. Yang, Q. Hu, Z. Cai, L.-M. Liu and L. Guo, Recent Progress of Amorphous Nanomaterials, Chem. Rev., 2023, 123, 8859–8941.
32. J. Strand and A. L. Shluger, On the Structure of Oxygen Deficient Amorphous Oxide Films, Adv. Sci., 2024, 11, 2306243.
33. A. Liu, Y.-S. Kim, M. G. Kim, Y. Reo, T. Zou, T. Choi, S. Bai, H. Zhu and Y.-Y. Noh, Selenium-alloyed tellurium oxide for amorphous p-channel transistors, Nature, 2024, 629, 798–802.
34. A. Aliano, A. Catellani and G. Cicero, Characterization of amorphous In₂O₃: An ab initio molecular dynamics study, Appl. Phys. Lett., 2011, 99, 211913.
35. D. B. Buchholz, Q. Ma, D. Alducin, A. Ponce, M. Jose-Yacaman, R. Khanal, J. E. Medvedeva and R. P. H. Chang, The Structure and Properties of Amorphous Indium Oxide, Chem. Mater., 2014, 26, 5401–5411.
36. K. Momma and F. Izumi, VESTA: a three-dimensional visualization system for electronic and structural analysis, J. Appl. Cryst., 2008, 41, 653–658.
37. V. Wang, N. Xu, J.-C. Liu, G. Tang and W.-T. Geng, VASPKIT: A user-friendly interface facilitating high-throughput computing and analysis using VASP code, Comput. Phys. Commun., 2021, 267, 108033.
38. B. Ryu, H.-K. Noh, E.-A. Choi and K. J. Chang, O-vacancy as the origin of negative bias illumination stress instability in amorphous In–Ga–Zn–O thin film transistors, Appl. Phys. Lett., 2010, 97, 022108.
39. K. Ide, K. Nomura, H. Hosono and T. Kamiya, Electron. Defects Amorphous Oxide Semicond., 2019, 216, 1800372.
40. S. Parthiban and J.-Y. Kwon, Role of dopants as a carrier suppressor and strong oxygen binder in amorphous indium-oxide-based field effect transistor, J. Mater. Res., 2014, 29, 1585–1596.
41. Z.-H. Li, T.-C. Chiang, P.-Y. Kuo, C.-H. Tu, Y. Kuo and P.-T. Liu, Heterogeneous Integration of Atomically-Thin Indium Tungsten Oxide Transistors for Low-Power 3D Monolithic Complementary Inverter, Adv. Sci., 2023, 10, 2205481.
42. W. Ma, Z. Ren, H. Shi, X. Xia, X. Wang, H. Ji, H. Chen, C. Luo, C. Wang, S. Chen and Y. Chen, Manganese Doped Tin Oxide for Stable and Efficient Quantum Dot Light–Emitting Diodes, Laser Photonics Rev., 2024, 18, 2400005.
43. T. Koida, Amorphous and crystalline In₂O₃-based transparent conducting films for photovoltaics, Phys. Status Solidi A, 2017, 214, 1600464.
44. N. Beji, M. Souli, S. Azzaza, S. Alleg and N. Kamoun Turki, Study on the zinc doping and annealing effects of sprayed In₂O₃ thin films, J. Mater. Sci.: Mater. Electron., 2016, 27, 4849–4860.
45. S. Li, Z. Shi, Z. Tang and X. Li, Comparison of ITO, In₂O₃:Zn and In₂O₃:H transparent conductive oxides as front electrodes for silicon heterojunction solar cell applications, Vacuum, 2017, 145, 262–267.
46. H.-W. Fang, T.-E. Hsieh and J.-Y. Juang, Effects of indium concentration on the efficiency of amorphous In–Zn–O/SiOx/n-Si hetero-junction solar cells, Solar Energy Mater. Solar Cells, 2014, 121, 176–181.
47. D. Kim, H. Lee, B. Kim, S. Baang, K. Ejderha, J.-H. Bae and J. Park, Investigation on Atomic Bonding Structure of Solution-Processed Indium-Zinc-Oxide Semiconductors According to Doped Indium Content and Its Effects on the Transistor Performance, Materials, 2022, 15, 6763.
48. W. Lin, R. Ma, J. Xue and B. Kang, RF magnetron sputtered ZnO:Al thin films on glass substrates: A study of damp heat stability on their optical and electrical properties, Solar Energy Mater. Solar Cells, 2007, 91, 1902–1905.
49. J. I. Kim, W. Lee, T. Hwang, J. Kim, S.-Y. Lee, S. Kang, H. Choi, S. Hong, H. H. Park, T. Moon and B. Park, Quantitative analyses of damp-heat-induced degradation in transparent conducting oxides, Solar Energy Mater. Solar Cells, 2014, 122, 282–286.
50. H. Hosono, Amorphous Oxide Semiconductors, John Wiley & Sons, Ltd, 2022, pp. 1–20.
51. Z. Pan, Y. Hu, J. Chen, F. Wang, Y. Jeong, D. P. Pham and J. Yi, Approaches to Improve Mobility and Stability of IGZO TFTs: A Brief Review, Trans. Electr. Electron. Mater., 2024, 25, 371–379.
52. Z. Gao, C. Han, J. Pan, J. Shen, Z. Liu, K. Chen, Z. Yi, Y. Zhang, Z. Yu, X. Zhou and P. Gao, Source Material Design for Realizing >50% Indium-Saving Transparent Electrode toward Sustainable Development of Silicon Heterojunction Solar Cells, ACS Appl. Mater. Interfaces, 2025, 17, 3265–3277.
53. Q. Shangguan, Y. Lv and C. Jiang, A Review of Wide Bandgap Semiconductors: Insights into SiC, IGZO, and Their Defect Characteristics, Nanomaterials, 2024, 14, 1679.
54. S.-J. Park and T.-J. Ha, Effects of Sn Doping on the Electrical Performance and Stability of Sub-V Operating Metal-Oxide Thin-Film Transistors Fabricated by Oxygen Annealing, IEEE Electron Device Lett., 2023, 44, 642–645.
55. J. Lee, C. H. Choi, T. Kim, J. Hur, M. J. Kim, E. H. Kim, J. H. Lim, Y. Kang and J. K. Jeong, Hydrogen-Doping-Enabled Boosting of the Carrier Mobility and Stability in Amorphous IGZTO Transistors, ACS Appl. Mater. Interfaces, 2022, 14, 57016–57027.
56. I. M. Choi, M. J. Kim, N. On, A. Song, K.-B. Chung, H. Jeong, J. K. Park and J. K. Jeong, Achieving High Mobility and Excellent Stability in Amorphous In–Ga–Zn–Sn–O Thin-Film Transistors, IEEE Trans. Electron Devices, 2020, 67, 1014–1020.
57. Z. Liu, C. Han, Z. Gao, X. Tan, J. Pan, X. Yin, K. Chen, Z. Yi, Y. Zhang, Z. Yu and P. Gao, Eliminating Mobility-Thickness Dependence in Transparent Conductive Oxide Layer Growth: A Critical Nucleation Strategy, Adv. Mater., 2025, e07648.
58. R. B. M. Cross and M. M. De Souza, Investigating the stability of zinc oxide thin film transistors, Appl. Phys. Lett., 2006, 89, 263513.
59. N. N. Mude, R. N. Bukke, J. K. Saha, C. Avis and J. Jang, Highly Stable, Solution-Processed Ga-Doped IZTO Thin Film Transistor by Ar/O₂ Plasma Treatment, Adv. Electron. Mater., 2019, 5, 1900768.
60. T.-T. Yang, D.-H. Kuo and K.-P. Tang, n-type Sn substitution in amorphous IGZO film by sol-gel method: A promoter of hall mobility up to 65 cm² V⁻¹ s⁻¹, J. Non-Cryst. Solids, 2021, 553, 120503.
61. B. J. Park, S. W. Chung, M. J. Kim, H. J. Lee, J. H. Bae, S. C. Kang and J. K. Jeong, Achieving High Field-Effect Mobility Exceeding 90 cm² V⁻¹ s⁻¹ in a-IGZTO Transistors With Excellent Reliability, IEEE Electron Device Lett., 2023, 44, 1857–1860.

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