Indium–gallium–zinc oxide (IGZO) films, deposited by sputtering at room temperature, still require activation to achieve satisfactory semiconductor characteristics. Thermal treatment is typically carried out at temperatures above 300 °C. Here, we propose activating sputter- processed IGZO films using simultaneous ultraviolet and thermal (SUT) treatments to decrease the required temperature and enhance their electrical characteristics and stability. SUT treatment effectively decreased the amount of carbon residues and the number of defect sites related to oxygen vacancies and increased the number of metal oxide (M–O) bonds through the decomposition-rearrangement of M–O bonds and oxygen radicals. Activation of IGZO TFTs using the SUT treatment reduced the processing temperature to 150 °C and improved various electrical performance metrics including mobility, on-off ratio, and threshold voltage shift (positive bias stress for 10,000 s) from 3.23 to 15.81 cm2/Vs, 3.96 × 107 to 1.03 × 108, and 11.2 to 7.2 V, respectively.
We developed a method to improve the electrical performance and stability of passivated amorphous In-Ga-Zn-O thin-film transistors by simultaneous ultraviolet and thermal (SUT) treatment. SUT treatment was carried out on fully fabricated thin-film transistors, including deposited source/drain and passivation layers. Ultraviolet (UV) irradiation disassociated weak and diatomic chemical bonds and generated defects, and simultaneous thermal annealing rearranged the defects. The SUT treatment promoted densification and condensation of the channel layer by decreasing the concentration of oxygen-vacancy-related defects and increasing the concentration of metal-oxide bonds. The SUT-treated devices exhibited improved electrical properties compared to nontreated devices: field-effect mobility increased from 5.46 to 13.36 V·s, sub-threshold swing decreased from 0.49 to 0.32 V/decade, and threshold voltage shift (for positive bias temperature stress) was reduced from 5.1 to 1.9 V.
We investigated the use of high-pressure gases as an activation energy source for
amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs).
High-pressure annealing (HPA) in nitrogen (N2) and oxygen (O2)
gases was applied to activate a-IGZO TFTs at 100 °C at
pressures in the range from 0.5 to 4 MPa. Activation of the a-IGZO TFTs
during HPA is attributed to the effect of the high-pressure environment, so that the
activation energy is supplied from the kinetic energy of the gas molecules. We
reduced the activation temperature from 300 °C to
100 °C via the use of HPA. The electrical characteristics of
a-IGZO TFTs annealed in O2 at 2 MPa were superior to those
annealed in N2 at 4 MPa, despite the lower pressure. For
O2 HPA under 2 MPa at 100 °C, the
field effect mobility and the threshold voltage shift under positive bias stress
were improved by 9.00 to 10.58 cm2/V.s and 3.89 to
2.64 V, respectively. This is attributed to not only the effects of the
pressurizing effect but also the metal-oxide construction effect which assists to
facilitate the formation of channel layer and reduces oxygen vacancies, served as
electron trap sites.
This study reports a low‐temperature processable, resistive switching (RS) device based on an inorganic–organic hybrid perovskite, i.e., methylammonium lead iodide (CH3NH3PbI3 or MAPbI3) via a fast deposition–crystallization method, as the multifunctional insulator layer to form metal/insulator/metal structure in which Al and p+‐Si wafer are used as the top and the bottom metal electrodes, respectively. The MAPbI3‐RS device shows acceptable RS characteristics with a switching window of 103 at a low voltage region (≈5 V), a stable endurance during 200 cycles, and a high retention for a prolonged time at 104 s. The operation mechanism of the MAPbI3‐RS device is based on ion (simultaneously vacancy) migration, especially iodine ions, which is analogous to that of oxygen ions in the conventional oxide‐based RS devices, confirmed through X‐ray photoelectron spectroscopy and energy‐dispersive X‐ray spectroscopy measurements. Furthermore, unusual multiresistance states are achieved from the MAPbI3‐RS device under light illumination due to the photosensitivity of MAPbI3.
We present a solution-processed
oxide absorption layer (SAL) for detecting visible light of long wavelengths
(635 and 532 nm) for indium–gallium–zinc oxide (IGZO)
phototransistors. The SALs were deposited onto sputtered IGZO using
precursor solutions composed of IGZO, which have the same atomic configuration
as that of the channel layer, resulting in superior interface characteristics.
We artificially generated subgap states in the SAL using a low annealing
temperature (200 °C), minimizing the degradation of the electrical
characteristics of thin-film transistor. These subgap states improved
the photoelectron generation in SALs under visible light of long wavelength
despite the wide band gap of IGZO (∼3.7 eV). As a result, IGZO
phototransistors with SALs have both high optical transparency and
superior optoelectronic characteristics such as a high photoresponsivity
of 206 A/W and photosensitivity of ∼106 under the
influence of a green (532 nm) laser. Furthermore, endurance tests
proved that the IGZO phototransistor with SALs can operate stably
under red laser illumination switched on and off at 0.05 Hz for 7200
s.
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