High-mobility ZrInO thin-film transistor prepared by an all-DC-sputtering method at room temperature

High-Performance Indium Gallium Tin Oxide Transistors with an Al2O3 Gate Insulator Deposited by Atomic Layer Deposition at a Low Temperature of 150 °C: Roles of Hydrogen and Excess Oxygen in the Al2O3 Dielectric Film

In this work, high-performance amorphous In_0.75Ga_0.23Sn_0.02O (a-IGTO) transistors with an atomic layer-deposited Al₂O₃ dielectric layer were fabricated at a maximum processing temperature of 150 °C. Hydrogen (H) and excess oxygen (O_i) in the Al₂O₃ film, which was controlled by adjusting the oxygen radical density (P_O2: flow rate of O₂/[Ar+O₂]) in the radio-frequency (rf) plasma during ALD growth of Al₂O₃, significantly affected the performance and stability of the resulting IGTO transistors. The concentrations of H and O_i in Al₂O₃/IGTO stacks according to P_O2 were characterized by secondary ion mass spectroscopy, X-ray photoelectron spectroscopy, hard X-ray photoemission spectroscopy, and thermal desorption spectroscopy. The high concentration of H at a low P_O2 of 2.5% caused heavy electron doping in the underlying IGTO during thermal annealing at 150 °C, leading to a conductive behavior in the resulting transistor without modulation capability. In contrast, a high P_O2 condition of 20% introduced O₂ molecules (or O_i) into the Al₂O₃ film, which negatively impacted the carrier mobility and caused anomalous photo-bias instability in the IGTO transistor. Through in-depth understanding of how to manipulate H and O_i in Al₂O₃ by controlling the P_O2, we fabricated high-performance IGTO transistors with a high field-effect mobility (μ_FE) of 58.8 cm²/Vs, subthreshold gate swing (SS) of 0.12 V/decade, threshold voltage (V_TH) of 0.5 V, and I_ON/OFF ratio of ∼10⁹ even at the maximum processing temperature of 150 °C. Simultaneously, the optimized devices were resistant to exposure to external positive gate bias stress (PBS) and negative bias stress (NBS) for 3600 s, where the V_TH shifts for exposure to PBS and NBS for this duration were 0.1 V and -0.15 V, respectively.

High-Performance All-Solution-Processed Flexible Photodetector Arrays Based on Ultrashort Channel Amorphous Oxide Semiconductor Transistors

Amorphous oxide semiconductor (AOS) field-effect phototransistors (FEPTs) are promising candidates for emerging photodetectors. Unfortunately, traditional lateral AOS FEPTs suffer from low photosensitivity, slow response time and inadequate mechanical flexibility, which restrict their widespread commercial application. In this work, novel AOS-based vertical field-effect phototransistor (VFEPT) arrays are presented, where the semiconducting layer and source and drain electrodes are deposited by inkjet printing. Benefitted from the unique vertical structure and ultrashort channel length, the exciton dissociation, carrier transfer, and collection efficiency were dramatically enhanced, resulting in excellent photoelectric performance in VFEPT devices, which was better than that of the traditional lateral AOS phototransistors. Moreover, flexible AOS VFEPT arrays were investigated for the first time on polyimide substrates. Due to the unique vertical architecture, the carrier transport was negligibly affected by the strain-induced in-plane cracks of the semiconductor channel layer during the mechanical bending process, which overcame the maximum bending limit of traditional lateral AOS thin-film transistors to ensure a transistor technique that gives notable mechanical robustness against repeated mechanical bending. Hence, this work provided a new pathway in emerging applications for AOS photodetectors with sensitivity, transparency, and flexibility.

High-Performance Thin Film Transistor with an Neodymium-Doped Indium Zinc Oxide/Al₂O₃ Nanolaminate Structure Processed at Room Temperature

In this work, a high-performance thin film transistor with an neodymium-doped indium zinc oxide (Nd:IZO) semiconductor via a room temperature approach and adopting the Nd:IZO/Al₂O₃ nanolaminate structure was investigated. The effects of the ultrathin Al₂O₃ layer and the thickness of Nd:IZO layer in the nanolaminate structure on the improvement of electrical performance and stability of thin film transistors (TFTs) were systematically studied. Besides the carrier movement confined along the near-channel region, driven by the Al₂O₃ layer under an electrical field, the high performance of the TFT is also attributed to the high quality of the 8-nm-thick Nd:IZO layer and the corresponding optimal Nd:IZO/Al₂O₃ interface, which reduce the scattering effect and charge trapping with strong M–O bonds in bulk and the back-channel surface of Nd:IZO, according to the X-ray reflectivity (XRR), X-ray photoelectron spectroscopy (XPS), and micro-wave photo conductivity decay (μ-PCD) results. As a result, the Nd:IZO/Al₂O₃ TFT exhibits an outstanding performance, with a high μ_sat of 32.7 cm²·V⁻¹·s⁻¹, an I_on/I_off of 1.9 × 10⁸, and a low subthreshold swing (SS) value of 0.33 V·dec⁻¹, which shows great potential for the room temperature fabrication of TFTs in high-resolution or high-frame-rate displays by a scalable, simple, and feasible approach.

Room-Temperature Fabricated Thin-Film Transistors Based on Compounds with Lanthanum and Main Family Element Boron

For the first time, compounds with lanthanum from the main family element Boron (LaB_x) were investigated as an active layer for thin-film transistors (TFTs). Detailed studies showed that the room-temperature fabricated LaB_x thin film was in the crystalline state with a relatively narrow optical band gap of 2.28 eV. The atom ration of La/B was related to the working pressure during the sputtering process and the atom ration of La/B increased with the increase of the working pressure, which will result in the freer electrons in the LaB_x thin film. LaB_x-TFT without any intentionally annealing steps exhibited a saturation mobility of 0.44 cm²·V⁻¹·s⁻¹, which is a subthreshold swing (SS) of 0.26 V/decade and a I_on/I_off ratio larger than 10⁴. The room-temperature process is attractive for its compatibility with almost all kinds of flexible substrates and the LaB_x semiconductor may be a new choice for the channel materials in TFTs.