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This study investigates how ambient/carrier gases affect the material characteristics of amorphous indium–gallium–zinc oxide (a-InGaZnO) thin films deposited using the ultrasonic spray pyrolysis deposition (USPD) method. Nitrogen and air are used as the ambient/carrier gases in this study. The crystallinity, oxygen deficiency, energy bandgap, and trap level in the a-InGaZnO thin films are analyzed. The performance of the thin-film transistors (TFTs) based on a-InGaZnO with different ambient/carrier gases is investigated as well. It is found that oxygen deficiency is suppressed when air is used as the ambient/carrier gas. When nitrogen is used as the ambient/carrier gas to deposit a-InGaZnO thin film, the TFT shows higher field-effect mobility and saturation mobility. However, when the a-InGaZnO thin film is deposited with air as the ambient/carrier gas, the subthreshold swing, ON-/ OFF-current ratio, interface trap density, and stability of the TFT are improved. This study demonstrates how ambient/carrier gases in the USPD system affect the performance of a-InGaZnO TFT. [ABSTRACT FROM AUTHOR]

This study demonstrates an amorphous indium–tin–zinc–oxide (a-ITZO) thin-film transistor (TFT) using an ultrasonic spray pyrolysis deposition (USPD) method. X-ray diffraction, X-ray photoelectron spectroscopy, Tauc plot, and photoluminescence spectrum are used to confirm the crystal structure, oxygen contents, energy bandgap, and the existence of oxygen deficiencies. Besides, these material characteristics are compared with a sputter-deposited ITZO film. The TFT based on the USPD-deposited ITZO shows better electrical performance than the TFT based on the sputter-deposited ITZO. In addition, the negative- /positive-bias illumination stress results indicate that the TFT based on the USPD-deposited ITZO film is more stable than the one based on the sputter-deposited ITZO. [ABSTRACT FROM AUTHOR]

This article demonstrates a Mg0.4Zn0.6O-based ultraviolet-B photodiode using ultrasonic spray pyrolysis deposition (USPD). The material characteristics of the USPD-deposited Mg0.4Zn0.6O thin film are investigated by the X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence, and ellipsometer. Schottky photodiode is fabricated by using Pt as the anode and Ti/Au as the cathode. Note that 0.84-eV Schottky barrier height is formed between Pt and Mg0.4Zn0.6O. The present Schottky barrier photodiode shows high rectification ratio of 104 and high ultraviolet-to-visible rejection ratio of 1.83 × 105. Furthermore, the specific detectivity is over 1011 Jones at ultraviolet-B region. [ABSTRACT FROM AUTHOR]

A nonvacuum thin-film deposition technology called ultrasonic spray pyrolysis deposition method is used to deposit fluorine-doped tin oxide, Al2O3, and TiO2 thin films, both of which are further applied on the anatase TiO2-based thin-film phototransistors (PTs). The material characteristics of the anatase TiO2 such as selected area electron diffraction, X-ray photoelectron spectroscopy, photoluminescence spectrum, and deep-level transient spectroscopy are investigated. The anatase TiO2-based thin-film PTs have a maximum output current of 4.56 mA/mm, subthreshold swing of 171 mV/dec, and threshold voltage of 0.7 V. The photoresponse characteristics of the anatase TiO2-based thin-film PTs at different quiescent-points are measured and investigated. It is found that the present anatase TiO2-based thin-film PTs can be operated in three different modes depending on the $\text{V}_{\text {DS}}$ and $\text{V}_{\text {GS}}$ biasing. In high-responsivity mode, the responsivity is 32.06 A/W; in high detectivity mode, the detectivity is $1.98 \times 10^{10}$ Jones; and in high ultraviolet (UV)-to-visible rejection ratio mode, the UV-to-visible rejection ratio is 1600. [ABSTRACT FROM AUTHOR]

This paper presents an MgO thin films deposited by an ultrasonic spray pyrolysis deposition method to serve as passivation and antireflection layers of the InGaN/GaN light-emitting diodes (LEDs). The electrical, electroluminescence (EL), and efficiency characteristics of the LEDs with 60-, 70-, and 80-nm MgO films are investigated. It is found that the LEDs with the MgO films have lower reverse currents and higher shunt resistance than that without an MgO film. However, there are no significant differences of the forward voltage at 350 mA and the series resistance between the LEDs with and without the MgO films. The significant differences between the LEDs with and without the MgO films are the light output power (LOP) and efficiency. The LED with 70-nm MgO film has the highest LOP of 556 mW (at 700 mA) and external quantum efficiency of 40.8% (at 30 mA). Further, the LED chips with the MgO films show better LOP and wall plug efficiency than those with the SiO2 and SiNx films. It is also found that the LED chips with MgO film as a passivation layer shows stable electrical and EL characteristics in the aging time test. [ABSTRACT FROM PUBLISHER]

Anatase and rutile TiO2-based metal–semiconductor–metal (MSM) ultraviolet photodetectors (PDs) are fabricated and investigated. The TiO2 thin films are grown by the ultrasonic spray pyrolysis deposition and the TiO2 films are annealed at 400 °C and 800 °C to form the anatase and the rutile phases. The material characteristics were measured by X-ray diffraction, Raman spectrum, X-ray photoelectron spectroscopy, and photoluminescence. The optical characteristics such as refractive index, extinction coefficient, absorption coefficient, and optical reflectance were characterized. The electrical and optoelectronic characteristics of the anatase and rutile TiO2 MSM PDs were characterized, including current-voltage, Schottky barrier height, spectral responsivity, response time, and detectivity. [ABSTRACT FROM AUTHOR]

Comparative studies for TiO2-passivated Al0.25Ga0.75N/GaN heterostructure FETs (HFETs) and TiO2-dielectric MOS-HFETs using nonvacuum ultrasonic spray pyrolysis deposition technique are made. Optimum device performances are obtained by tuning the layer thickness of TiO2 to 20 nm. High relative permittivity ( k ) of 53.6 and thin effective oxide thickness of 1.45 nm are also obtained. Pulse-IV, Hooge coefficient ( \alpha _{H} ), Transmission Electron Microscopy, and atomic force microscope have been performed to characterize the interface, atomic composition, and surface flatness of the TiO2 oxide. Superior improvements for the present TiO2-dielectric MOS-HFET/TiO2-passivated HFETs are obtained, including 47.6%/23.8% in two-terminal gate–drain breakdown voltage (BV _{\rm GD}) , 111%/22.2% in two-terminal gate-drain turn-ON voltage ( V\mathrm{{\scriptscriptstyle ON}}) , 47.9%/39.4% in ON-state breakdown (BV DS) , 12.2%/10.2% in drain–source current density ( IDS) at VGS = 0 V ( IDSS0) , 27.2%/11.7% in maximum IDS ( IDS, max) , 3/1-order enhancement in on/off current ratio ( I\mathrm{{\scriptscriptstyle ON}} / I\mathrm{{\scriptscriptstyle OFF}}) , 58.8%/17.6% in gate-voltage swing linearity, 25.1%/13.2% in unity-gain cutoff frequency ( fT) , 40.6%/24.7% in maximum oscillation frequency ( f\max ) , and 33.8%/15.6% in power-added efficiency with respect to a Schottky-gated HFET fabricated on the identical epitaxial structure. The present MOS-HFET has also shown stable electrical performances when the ambient temperature is varied from 300 to 450 K. [ABSTRACT FROM AUTHOR]