In this study, we proposed β-Ga₂O₃ JFET using nitrogen doping and analyzed the electrical characteristics. In β-Ga₂O₃, nitrogen ions act as a deep acceptor and are used to implement the current blocking layer. By using this characteristic of the nitrogen ion, in the proposed JFET, nitrogen ions are used to obtain gate control and pinch off the channel of the JFET. The numerical TCAD simulation was performed to design and analyze the proposed JFET. The simulated forward and reverse characteristics of the proposed JFET were obtained as a function of JFET width and nitrogen doping concentration. The maximum breakdown voltage of 1.7 kV was obtained with the on-resistance of 16.7 mΩ·cm2 when the channel width was 1.5 μm and nitrogen doping concentration is 1×1018/cm3, respectively.
Next-generation wide-bandgap semiconductors such as SiC, GaN, and Ga2O3 are being considered as potential replacements for current silicon-based power devices due to their high mobility, larger size, and production of high-quality wafers at a moderate cost. In this study, we investigate the gradual modulation of chemical composition in multi-stacked metal oxide semiconductor thin films to enhance the performance and bias stability of thin-film transistors (TFTs). It demonstrates that adjusting the Ga ratio in the indium gallium oxide (IGO) semiconductor allows for precise control over the threshold voltage and enhances device stability. Moreover, employing multiple deposition techniques addresses the inherent limitations of solution-processed amorphous oxide semiconductor TFTs by mitigating porosity induced by solvent evaporation. It is anticipated that solution-processed indium gallium oxide (IGO) semiconductors, with a Ga ratio exceeding 50%, can be utilized in the production of oxide semiconductors with wide band gaps. These materials hold promise for power electronic applications necessitating high voltage and current capabilities.
Oxide semiconductor gas sensors are widely used for detecting toxic, explosive, and flammable gases due to their simple structure, cost-effectiveness, and potential integration into compact devices. However, their reliable gas detection is hindered by a longstanding issue known as humidity dependence, wherein the sensor resistance and gas response change significantly in the presence of moisture. This problem has persisted since the inception of oxide semiconductor gas sensors in the 1960s. This paper explores the root causes of humidity dependence in oxide semiconductor gas sensors and presents strategies to address this challenge. Mitigation strategies include functionalizing the gas-sensing material with noble metal/transition metal oxides and rare-earth/rare-earth oxides, as well as implementing a moisture barrier layer to prevent moisture diffusion into the gas-sensing film. Developing oxide semiconductor gas sensors immune to humidity dependence is expected to yield substantial socioeconomic benefits by enabling medical diagnosis, food quality assessment, environmental monitoring, and sensor network establishment.
The transfer characteristics of amorphous indium gallium zinc oxide thin film transistor (a-IGZO TFT) showed the distortion in the subthreshold region after gate bias stress, in addition to the parallel shift of threshold voltage. The capacitancevoltage (C-V) curve was also deformed from its initial shape after the gate bias stress. This study analyzes both the C-V and transfer curves plotted on the same gate voltage axis in order to investigate the mechanism driving the distortion in the transfer curve. It is deduced that an additional interfacial trap states at the bottom interface of a-IGZO are produced during gate bias stress, thereby they exhibit the back channel effect, which explains the origin of the distortion in the transfer curve and the deformation of C-V curve.
Developing a thin-film transistor with characteristics such as a large area, high mobility, and high reliability are key elements required for the next generation on displays. In this paper, we have investigated the research trends related to improving the reliability of oxide-semiconductor-based thin-film transistors, which are the primary focus of study in the field of optical displays. It has been reported that thermal treatment in a high-pressure oxygen atmosphere reduces the threshold voltage shift from -7.1 V to -1.9 V under NBIS. Additionally, a device with a SiO2/Si3N4 dual-structure has a lower threshold voltage (-0.82 V) under NBIS than a single-gate-insulator-based device (-11.6 V). The dual channel structure with different oxygen partial pressures was also confirmed to have a stable threshold voltage under NBIS. These can be considered for further study to improve the NBIS problem.
We investigated the electrical characteristics of amorphous silicon-zinc-tin-oxide (a-SZTO) thin films deposited by RF-magnetron sputtering at room temperature depending on the deposition time. We fabricated a thin film transistor (TFT) with a bottom gate structure and various channel thicknesses. With increasing channel thickness, the threshold voltage shifted negatively from -0.44 V to -2.18 V, the on current (Ion) and field effect mobility (μFE) increased because of increasing carrier concentration. The a-SZTO film was fabricated and analyzed in terms of the contact resistance and channel resistance. In this study, the transmission line method (TLM) was adopted and investigated. With increasing channel thickness, the contact resistance and sheet resistance both decreased.
This research introduces the sputtered IZO thin film transistor (TFT) with solution-processed Al2O3 diffusion layer. IZO is one of the most commonly used amorphous oxide semiconductor (AOS) TFT. However, most AOS TFTs have many defects that degrade performance. Especially oxygen vacancy in the active layer. In previous research, aluminum was used as a carrier suppressor by binding the oxygen vacancy and making a strong bond with oxygen atoms. In this paper, we use a solution-processed Al2O3 diffusion layer to fabricate stable IZO TFTs. A double-layer solution-processed Al2O3-sputtered IZO TFT showed better performance and stability, compared to normal sputtered IZO TFT.
We investigated solution-processed indium-yttrium-oxide (IYO) TFTs using apoly (methyl methacrylate) (PMMA) passivation layer. The IYO semiconductor solution was prepared with 0.1 M indium nitrate hydrate and 0.1 M yttrium acetate dehydrate as precursor solutions. The solution-processed IYO TFTs showed good performance: field-effect mobility of 13.13 ㎠/Vs, a threshold voltage of 8.2 V, a subthreshold slope of 0.93 V/dec, and a current on-to-off ratio of 7.2 × 106. Moreover, the PMMA passivation layers used to protectthe IYO active layer of the TFTs, did so without deteriorating their performance under ambient conditions; their operational stability and electrical properties also improved by decreasing leakage current.
We report on amorphous thin-film transistors (TFTs) with indium zinc oxide (IZO) channel layers that were fabricated via a solution process. We prepared the IZO semiconductor solution with 0.1 M indium nitrate hydrate and 0.1 M zinc acetate dehydrate as precursor solutions. The solution- processed IZO TFTs showed good performance: a field-effect mobility of 7.29 ㎠/Vs, a threshold voltage of 4.66 V, a subthreshold slope of 0.48 V/dec, and a current on-to-off ratio of 1.62×105. To investigate the static response of our solution-processed IZO TFTs, simple resistor load-type inverters were fabricated by connecting a 2-MΩ resistor. Our IZOTFTbased N-MOS inverter performed well at operating voltage, and therefore, isa good candidate for advanced logic circuits and display backplane.
In this study, we fabricated a TFT gas sensor with ZnO nanorods grown by hydrothermal synthesis. The suggested devices were compared with the conventional ZnO film-type TFTs in terms of the gas-response properties and the electrical transfer characteristics. The ZnO seed layer is formed by atomic-layer deposition (ALD), and the precursors for the nanorods are zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and hexamethylenetetramine ((CH2)6N4). When 15 ppm of NO gas was supplied in a gas chamber at 150°C to analyze the sensing capability of the suggested devices, the sensitivity (S) was 4.5, showing that the nanorod-type devices respond sensitively to the external environment. These results can be explained by X-ray photoelectron spectroscopy (XPS) analysis, which showed that the oxygen deficiency of ZnO nanorods is higher than that of ZnO film, and confirms that the ZnO nanorod-type TFTs are advantageous for the fabrication of high-performance gas sensors.
The effect of low temperature (250℃) heat treatment after electron irradiation (irradiation time = 30, 180, 300s) on the chemical bonding and electrical properties of ZnO thin films prepared using a sol-gel process were examined. XPS (X-ray photoelectron spectroscopy) analysis showed that the electron beam irradiation decreased the concentration of M-O bonding and increased the OH bonding. As a result of the electron beam irradiation, the carrier concentration of ZnO films increased. The on/off ratio was maintained at ~105 and the VTH values shifted negatively from 11 to 1 V. As the irradiation time increased from 0 to 300s, the calculated S. S. (subthreshold swing) of ZnO TFTs increased from 1.03 to 3.69 V/decade. These values are superior when compared the sample heat-treated at 400℃ representing on/off ratio of ~102 and S. S. value of 10.40 V/decade.
NiO serves as a window layer for Si photoelectric devices. Due to the wide energy bandgap of NiO, high optical transparency (over 80%) was achieved and applied for Si photoelectric devices. Due to the high the high mobility, the heterojunction device (Al/n-Si/SiO2/p-NiO/ITO) provide ultimately fast photoresponses of rising time of 38.33 μs and falling time of 39.25 μs, respectively. This functional NiO layer would provide benefits for high-performing photoelectric devices, including photodetectors and solar cells.
Next-generation displays should be transparent and flexible as well as having high resolution and frame number. The main factor for active matrix organic light emitting diode and next-generation displays is the development of TFTs (thin-film transistors) with high mobility and large area uniformity. The TFTs used for transparent displays are mainly oxide TFT that has oxide semiconductor as channel layer. Zinc-oxide based substances such as indium-gallium-zinc-oxide has attracted attention in the display industry. In this paper, the mobility improvement of low cost oxide TFT is studied for fast operating next-generation displays by overcoming disadvantages of amorphous silicon TFT that has low mobility and poly silicon TFT that requires expensive equipment for complex process and doping process.
MgZnO has attracted a lot of attention for flexible device. In the flexible substrate, the crystalstructure of the thin films as well as the surface morphology is not good. Therefore, in this study, westudied on the effects of the oxygen pressure on the structure and crystallinity of Mg0.3Zn0.7O thin films deposited on PES substrate by using pulsed laser deposition. We used X-ray diffraction and atomic forcemicroscopy in order to observe the structural characteristics of Mg0.3Zn0.7O thin films. The crystallinity ofMg0.3Zn0.7O thin films with increasing temperature was improved, Grain size and RMS of the films wereincreased. UV-visible spectrophotometer was used to get the band gap energy and transmittance. Mg0.3Zn0.7O thin films showed high transmittance over 90% in the visible region. As increased workingpressure from 30 mTorr to 200 mTorr, the bandgap energy of Mg0.3Zn0.7O thin film were decreased from3.59 eV to 3.50 eV.
Transparent amorphous In-Si-O (ISO)/Ag/In-Si-O (ISO) has been reported for low emissivity(low-e) applications. Effective Si doping into the In2O3 matrix led to a completely amorphous ISO film aswell as a low resistivity and a high optical transmittance. The optical and electrical performances wereexamined by measuring transmittance with a UV-VIS spectrophotometer and resistivity with a Hall effectmeasurement. Consequently, low-e glass with ISO/Ag/ISO showed a high transparency in the visibleregion and low emissivity in the infrared region, indicating that ISO is a promising amorphoustransparent electrode for low-e glass.
Thin-film transistors(TFTs) with silicon-zinc-tin-oxide(SiZnSnO, SZTO) channel layer are fabricated by rf sputtering method. Electrical properties were changed by different annealing treatment of dry annealing and wet annealing. This procedure improves electrical property especially, stability of oxide TFT. Improved electrical properties are ascribed to desorption of the negatively charged oxygen species from the surfaces by annealing treatment. The threshold voltage (Vth) shifted toward positive as increasing Si contents in SZTO system. Because the Si has a lower standard electrode potential (SEP) than that that of Sn, Zn, resulting in the degeneration of the oxygen vacancy (Vo). As a result, the Si acts as carrier suppressor and oxygen binder in the SZTO as well as a Vib controller, resulting in the enhancement of stability of TFTs,
Thin-film transistors(TFTs) with silicon zinc tin oxide(SZTO) channel layer are fabricated by solution-process. The threshold voltage (Vth) shifted toward positive directly with increasing Si contents in SZTO system. Because the Si has a lower standard electrode potential (SEP) than Sn, Zn, thus degenerate the oxygen vacancy (VO). As a result, the Si act as carrier suppressor and oxygen binder in the SZTO as well as a Vth controller.
The effect of co-sputtering condition on the structural properties of Mg_xZn_1-xO thin films grown by RF magnetron co-sputtering system was investigated for manufacturing UV LED. Mg_xZn_1-xO thin films were grown with ZnO and MgO target varying RF power. Structural properties were investigated by X-ray diffraction (XRD) and Energy dispersive spectroscopy (EDS). The Mg_xZn_1-xO thin films have sufficient crystallinity on the high ZnO power. The EDS analyzed showed that the Mg content in the Mg_xZn_1-xO films decreased from 3.99 to 24.27 at.% as the RF power of ZnO target increased. The Mg content in the Mg_xZn_1-xO films could be controlled by co-sputtering power.
The dependency of annealing temperature on the electrical performances in amorphous silicon-zinc-tin-oxide thin film transistors (SZTO TFT) has been investigated. The SZTO channel layers were prepared by using radio frequency (RF) magnetron sputtering method with different annealing treatment. The field effect mobility (UFE) increased and threshold voltage (Vth) shifted to negative direction with increasing annealing temperature. As a result, oxygen vacancies generated in SZTO channel layer with increasing annealing temperature resulted in negative shift in V1h and increase in on-current.
The dependency of processing pressure on the electrical performances in amorphous silicon -zinc-tin-oxide thin film transistors (SZTO-TFT) has been investigated. The SZTO channel layers were deposited by using radio frequency (RF) magnetron sputtering method with different partial pressure. The field effect mobility (μFE) increased and threshold voltage (Vth) shifted to negative direction with increasing pressure during deposition processing. As a result, oxygen vacancies generated in SZTO channel layer with increasing partial pressure resulted in negative shift in Vth and increase in on-current.
Recently, amorphous oxide semiconductors (AOSs) based thin-film transistors (TFTs) have received considerable attention for application in the next generation displays industry. The research trends of AOSs based TFTs investigation have focused on the high device performance. The electrical properties of the TFTs are influenced by trap density. In particular, the threshold voltage (Vth) and subthreshold swing (SS) essentially depend on the semiconductor/gate-insulator interface trap. In this article, we investigated the effects of Ar plasma-treated SiO2 insulator on the interfacial property and the device performances of amorphous indium gallium zinc oxide (a-IGZO) TFTs. We report on the improvement in interfacial characteristics between a-IGZO channel layer and gate insulator depending on Ar power in plasma process, since the change of treatment power could result in different plasma damage on the interface.
Thin-film transistors(TFTs) with magnesium zinc tin oxide(MZTO) channel layer are fabricated by solution-process. The threshold voltage (Vth) shifted toward positive directly with increasing Mg contents in MZTO system. Because the Mg has a lower standard electrode potential (SEP) than Sn, Zn, thus degenerate the oxygen vacancy (VO). As a result, the Mg act as carrier suppressor and oxygen binder in the MZTO as well as a Vth controller.
The dependency of sputtering power on the electrical performances in amorphous HIZO-TFT (hafnium-indium-zinc-oxide thin film transistors) has been investigated. The HIZO channel layers were prepared by using radio frequency (RF) magnetron sputtering method with different sputtering power at room temperature. TOF-SIMS (time of flight secondary ion mass spectrometry) was performed to confirm doping of hafnium atom in IZO film. The field effect mobility (μFE) increased and threshold voltage (Vth) shifted to negative direction with increasing sputtering power. This result can be attributed to the high energy particles knocking-out oxygen atoms. As a result, oxygen vacancies generated in HIZO channel layer with increasing sputtering power resulted in negative shift in Vth and increase in on-current.
Soution-processed ZrInZnO (ZIZO) thin-film transistors (TFTs) with varying Zr content were fabricated. The ZIZO TFT (Zr=20 at. %/Zn) has an optimal performance with the saturation field effect mobility of 0.77 cm2/Vs, the threshold voltage (Vth) of 2.1 V, the on/off ratio of 4.95×10(6), and subthreshold swing (S.S) of 0.73 V/decade. Using this optimized ZIZO TFT, the positive and negative gate bias stress according to annealing temperature was also investigated. While the Vth shifts dramatically after 1,000 s of both gate bias stresses, variations in the S.S are negligible. It suggests that electrons or holes are temporarily trapped in the gate insulator, the semiconductor, or the interface between both layers.
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