This work presents growing amorphous, anatase, rutile, and mixed phases TiO2 thin films by mist chemical vapor deposition and post deposition annealing techniques. The annealing temperature affects crystal structures of the TiO2 films significantly. X-ray diffraction and Raman spectra are used to characterize the structures of the TiO2 films. X-ray photoelectron spectroscopy is used to analyze the chemical composition of the TiO2 film. The optical characteristics including refractive index, extinction coefficient, optical absorption coefficient, and photoluminescence spectrum are measured. Finally, the metal-semiconductor-metal photodetectors are fabricated and their current-voltage, Schottky barrier height, photoresponse characteristics, response time, and detectivity characteristics are investigated. The research results show that these crystal structures of the TiO2 demonstrate their specific advantages in the performance of the photodetectors.

This paper investigates the temperature-dependent performances of AlGaN/GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT). The gate dielectric layer and surface passivation layer are formed by the H ₂ O ₂ oxidation technique. The gate dielectric quality is estimated by the breakdown electric field (EBD) and low-frequency noise. The capacitance-voltage (C-V) hysteresis characteristics of MOS and Schottky diodes at 300/480 K are also studied. An appropriate thermal model is used to investigate the self-heating effect and calculate the effective channel temperature (T _eff ). The dc performances of the present MOS-HEMT are improved at 300/480 K, as compared with a Schottky-barrier HEMT (SB-HEMT), including output current density, maximum extrinsic transconductance (gm,max), gate voltage swing, gate-drain leakage current (IGD), specific ON-resistance (RON), three-terminal OFF-state breakdown voltage (BVOFF), and subthreshold swing. Factors that cause IGD and BVOFF are analyzed by the temperature-dependent measurement. The passivation effect of the present MOS-HEMT is also confirmed by the surface leakage measurement. The devised MOS-HEMT demonstrates superior thermal stability to the reference SB-HEMT. The present-design is promising for high-temperature electronic applications.

This study demonstrates a novel enhancementmode tri-gate nanowire InAlN/GaN MOSHEMT with ultrasonic spray pyrolysis deposition (USPD) deposited Al2O3 as the gate dielectric layer. The proposed device reveals a threshold voltage (VTH) of +2.3 V and a maximum drain current (ID, max) of 705 mA/mm. It also exhibits superior electrical performances, including a high on-state/off-state current (Ion/Ioff) ratio of 109-1010, a steep subthreshold swing (SS) of 65 mV/decade, and a large breakdown voltage (BV) of 800 V with a leakage current of 0.7 μA/mm while keeping a low specific on-resistance (Ron, sp) of 1.04 mΩ·cm2. This novel E-mode device presents great potential for power device applications.

This brief reports, for the first time, an oxide passivated AlGaN/GaN high electron mobility transistor by using the hydrogen peroxide (H₂O₂) treatment. Characterizations by using electron spectroscopy for chemical analysis and transmission electron microscopy have been performed to verify the formation of surface oxide on the AlGaN barrier layer. The present design has demonstrated superior improvements of 41% in the maximum drain/source current density I_DS,max; 39% in the drain/source saturation current density at zero gate bias I_DSSO, 47% in the maximum extrinsic transconductance g_m,max, 53.2% in the two-terminal gate/drain breakdown voltage BV_GD 36% in the cutoff frequency f_T, and 20% in the maximum oscillation frequency f_max, as compared with an unpassivated conventional device.

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.

Comparative studies for TiO ₂ -passivated Al _0.25 Ga _0.75 N/GaN heterostructure FETs (HFETs) and TiO ₂ -dielectric MOS-HFETs using nonvacuum ultrasonic spray pyrolysis deposition technique are made. Optimum device performances are obtained by tuning the layer thickness of TiO ₂ 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 (α _H ), Transmission Electron Microscopy, and atomic force microscope have been performed to characterize the interface, atomic composition, and surface flatness of the TiO ₂ oxide. Superior improvements for the present TiO2dielectric MOS-HFET/TiO ₂ -passivated HFETs are obtained, including 47.6%/23.8% in two-terminal gate-drain breakdown voltage (BV _GD ), 111%/22.2% in two-terminal gate-drain turnON voltage (V _ON ), 47.9%/39.4% in ON-state breakdown (BV _DS ), 12.2%/10.2% in drain-source current density (I _DS ) at V _GS = 0 V (I _DSS0 ), 27.2%/11.7% in maximum I _DS (I _DS,max ), 3/1-order enhancement in ON/OFF current ratio (I _ON /I _OFF ), 58.8%/17.6% in gate-voltage swing linearity, 25.1%/13.2% in unity-gain cutoff frequency (f _T ), 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.