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We have evaluated optical and electrical characteristics of Ga-Sn-O (GTO) films deposited using mist chemical vapor deposition (CVD). It was found that the GTO film is transparent, which suggests the energy gap is wide. The X-ray diffraction (XRD) indicated that the GTO film was crystallized, but the crystal structure is not clarified now. It was also found that the sheet resistance decreases as the...
We confirmed that photo-induced current in off region changes when we irradiate infrared light to N-type, P-type and PIN-type low-temperature poly-Si TFTs. In addition, we found that the photo-induced current is proportional to the gate width, whereas it does not depend on the gate length. We can indicate that it is possible to detect infrared light above certain intensity from the relationship between...
We have evaluated Ga-Sn-O (GTO) films fabricated using mist chemical vapor deposition (CVD). First, it is found that the GTO films are roughly transparent. Moreover, as the deposition temperature decreases, the transmittance becomes higher. Next, it is found that even if the carrier gas speed changes, the sheet resistance is roughly the same. However, as the composition ratio in the material solution...
We investigate MR effect of GTO thin-film devices. It is found positive and negative MR effects. Something dramatically changes in GTO thin-film devices. Moreover, it is suggested that the GTO thin-film devices with oxygen of high concentration indicate negative MR effect. This may be due to the generation of random potential and Anderson localization with oxygen. Finally, in the case of some special...
We have developed a hybrid-type temperature sensor using thin-film transistors generating rectangle output waveform. The advantages of the hybrid-type temperature sensor are that the large temperature dependence of the off-leakage current can be utilized, and simultaneously only a digital circuit is required to count the digital pulse. However, the conventional hybrid-type sensor has a disadvantage...
We have developed a hybrid-type temperature sensor using n-type low-temperature processed poly-Si thin-film transistors. The advantages of the hybrid-type temperature sensor are that the large temperature dependence of the off-leakage current can be utilized, and simultaneously only a digital circuit is required to count the digital pulse.
We have developed neuron MOS devices using TFTs. We fabricated and evaluated neuron MOS inverter, which can be also utilized as a variable threshold voltage inverter, and neuron MOS source follower, which can be also utilized as a digital-analog converter. The neuron MOS devices indicate that TFTs have great potential for application to artificial neural networks.
We have evaluated characteristic deviation and characteristic degradation of poly-Si thin-film phototransistors. We found that the characteristic deviation is not negligible, which seems due to energy distribution of excimer-laser crystallization, and must be compensated for some applications. We found that the characteristic degradation is negligible, which is convenient for abovementioned applications.
We fabricated a p-type poly-Si thin-film transistor with Hall terminals and evaluated the Hall voltage by applying gate voltage, drain voltage, and magnetic field. We found that the Hall voltage is dependent on the magnetic field when the gate voltage is beyond a threshold voltage.
Low temperature TFT was fabricated on SiOx insulator film deposited with novel line shaped plasma source, namely, facing electrodes CVD (FE-CVD). The plasma was generated with magnetic field and RF power source applied to the two facing SiO2 targets. The insulating film was deposited with mixture of tetramethylsilane and oxygen as source gases at high deposition rate at 11.6 nm/min. Insulating properties...
We have evaluated photoconductivities in diode connections using n-ch, p-ch, and pin-ch poly-Si TFTs for photosensor application. It is found that the photoconductivities increase as the illuminance increases for all the TFTs, but they do not change so much as the applied voltage changes. Moreover, the photoconductivities are: p-ch TFT < pin-ch TFT with the gate terminal to the p-type region <...
We have improved magnetic field sensitivities of poly-Si Hall devices by applying high voltages. We achieved the magnetic field sensitivity of 5.13 V/T by applying 580 V. This value is 1000 times higher than the previous magnetic field sensitivity.
We have evaluated multiple-input NAND circuits using polycrystalline silicon thin-film transistors and found that the output pulse became degraded for the 3-input NAND circuit. Moreover, we have fabricated a set-reset flip-flop (SR-FF) circuit using the 2-input NAND circuits and confirmed that the SR-FF circuit operated correctly.
The optoelectronic characteristic of a p-i-n thin-film phototransistor is analyzed by comparing an actual device with device simulation. It is found using the actual device that the detected current is maximized when the control voltage is equal to the applied voltage. It is also found using the device simulation that a depletion layer is widely formed at that voltage because the electron mobility...
Enhancement of subthreshold swing with increasing the channel layer thickness of bottom gate top contact type amorphous oxide TFT were evaluated by 2D device simulation with trap states induced in backchannel. The distance between the channel and the trap states induced in backchannel would be the main reason for the enhancement of the subthreshold swing. This effect is similar to one of the oxide...
We have developed a magnetic-field line sensor using poly-Si micro Hall devices. First, we fabricate the micro Hall devices using low-temperature poly-Si fabrication processes. Next, we measure the dependences of the Hall voltage (VH) on the magnetic field (B) for each micro Hall device and verify that VH is linear to B although VH has an offset voltage that varies among each device even if B is zero...
We propose a light irradiation history sensor using an amorphous In-Ga-Zn-O (α-IGZO) thin-film transistor (TFT) fabricated by high oxygen partial pressure sputtering. The α-IGZO TFT has an interesting property. The Ids-Vgs characteristic shifts positively, and the subthreshold slope becomes steep when the gate bias is applied, whereas the Ids-Vgs characteristic shifts negatively and the subthreshold...
Thin-film transistors (TFTs) are key devices for high image quality information displays. Features and applications of various TFTs, such as matured amorphous and poly-Si TFTs and transparent poly-ZnO and amorphous InGaZnO TFTs, are discussed.
A 2-D simulator of laser crystallization is proposed as a practical evaluation tool for polycrystalline-silicon thin-film transistors. Random nucleation, crystal growth velocity, latent heat emission, and partial crystallization are modeled to simulate crystallization processes from supercooling phases. Grain sizes are reproduced as a function of substrate temperature during laser crystallization...
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