Papers by Keyword: Thin Film Transistor

Abstract: Effect of storage in air on silicon doped indium oxide (In-Si-O) thin-film transistors fabricated via solution processing has been investigated. The on/off ratio drastically increased from 10¹ just after fabrication to 10⁵ on the 10-day storage, whereas the mobility slightly decreased from 1.4 cm²/Vs to 0.38 cm²/Vs. Time constant of aging effect was 3.6 days. The behavior suggests that oxygen defects in In-Si-O films, which may be produced during thermal evaporation of Al electrodes under high vacuum, are eliminated.

Abstract: With the widespread use of film transistors, amorphous oxide thin films have excellent transparency and conductivity, stable performance, smooth and smooth surface, easy to etch and large-area preparation, are compatible with existing processes, and do not require subsequent annealing to simplify the process. Process and other advantages have been applied to many fields such as thin film transistors. The principle of the amorphous oxide is basically the same as that of the crystalline state, Magnetron sputtering technology can prepare super-hard films, corrosion-resistant friction films, superconducting films, magnetic films, optical films, and various films with special functions. It is widely used in the field of industrial film preparation. This article focuses on the principle and characteristics of magnetron sputtering technology for electronic materials, the development history of magnetron sputtering technology and its development trend.

Abstract: To integrate circuits into the organic light emitting diode displays, it is necessary to fabricate polycrystalline silicon (poly-Si) based thin-film transistors (TFTs) on the glass substrates. In this work we investigated the correlation between the electrical characteristics and the poly-Si morphology of the excimer laser annealed (ELA) TFTs in ultralow oxygen concentrations (~ ppm). The main feature of ELA poly-Si films is the protrusion at grain boundaries that makes the film surface rough. The surface roughness increases with an increasing oxygen concentration during the laser annealing and degrades the TFT characteristics in the on-state as well as the breakdown voltage of the gate insulator, while the off current is independent of process conditions. This result is attributed to the increased oxygen incorporation in the film in the case of an ELA process. Since oxygen increased the defect density in the polysilicon bandgap, controlling the oxygen concentrations in the process chamber helped to improve the performance of the ELA poly-Si TFTs. Based on these results, we discuss the relationship between performance of active matrix organic light emitting display panels and oxygen concentrations during ELA.

Abstract: Temperature effect on the I-V characteristics of tin monoxide thin film transistors (SnO TFTs) has been analyzed. The result shows that the drain current of the SnO TFT obeys the Meyer-Neldel rule under low temperature, where current conduction is a thermally activated process. The carrier transport would be dominated by multiple trapping conduction, while, percolation conduction mechanism holds as the temperature increase.

Abstract: The paper presents some results on the effect of the metal electrode deposition on the electrical performance of amorphous polymthylmetacrylate (PMMA) thin films, measured in a MIM structure consisting of metal (Al)-insulator (PMMA)-metal (Ta). Aluminium (Al) electrode was deposited by physical vapor deposition method (PVD) on the top of PMMA film with the deposition rate of 5 and 10Å/s. The effect of aluminium deposition rate and post deposition annealing temperature on the morphology of the interface between Al electrode (100 or 300 nm thick) and PMMA thin film (40 or 70 nm thick) has been investigated by cross-section scanning electron microscopy (SEM). Based on SEM data, I-V characteristic measurements and dielectric constant values of insulating films, the deposition parameters of Al top-electrode was optimised. Our results showed that when the deposition of the Al electrode take place at a rate of 10 Å/s, no inter-diffusion or interfacial reaction at the interface between Al electrode and PMMA films were observed and the best delectric parameters of PMMA thin film were measured, which led to the best dielectric performance of PMMA layer in TFT configuration.

Abstract: Gallium-doped zinc oxide (GZO) thin films were fabricated by radio frequency (RF) magnetron sputtering on glass and silicon substrate at room temperature. The fabrication process, structure, optical properties, and electrical properties of the thin films with different powers (50 W, 70W, and 100 W) were studied to obtain more knowledge about the semiconductor performance. X-ray diffraction (XRD) analysis indicated that the GZO films were polycrystalline and preferred c axis orientation. The average transmittance decreased form 93% to 84% in the visible range, and all the optical band gap was about 3.05 eV when the power increased from 50W to 100W. Simultaneously, the GZO thin film transistors (TFTs) with excellent transfer characteristic prove that GZO thin film is a potential semiconductor material candidate which can be used for the active layer in thin film transistors fabrication.

Abstract: Indium-gallium-zinc oxide Thin Film Transistors (IGZO-TFT) were separately prepared with SiO_x and SiN_x/ SiO_x as gate insulator,with IGZO films deposited at room-temperature by RF magnetron sputtering method as active layer.Compared with TFT with SiO_x as gate insulator, The saturation mobility and the on/off ratio of TFT with SiN_x/ SiO_x as gate insulator were much higher. And,the threshold swing was also smaller.But,the threshold voltage was not good enough,was larger. By annealing at 200°C in the air,the saturation mobility increased from 1.42 to 7.5 cm².V^-1.S^-1. While, the saturation mobility had no obvious change when TFT was annealed at high temperature. Seriously, IGZO annealed at high temperature would become crystal,it was not good for the ohmic contact between active layer and metal conductive layer,and,the interface between active layer and insulator would be deteriorated.These will result in the threshold swing become larger and the on/off ratio get smaller.200°C is a suitable temperature for annealing. So,using SiN_x/ SiO_x films as gate insulator,together with TFT annealing at low temperature, could improve the performances of TFT effectively.

Abstract: The capacitance-voltage (C–V) characteristics of inverted staggered amorphous indium–gallium–zinc-oxide thin film transistors (α-IGZO TFTs) with various dimensions are investigated by physics-based technology computer aided design (TCAD) simulation. For gate bias lower than the threshold voltage of the TFT, the electrons in the channel region are nearly fully depleted. It causes that the total gate capacitance is determined by the overlap region of gate, α-IGZO, and source/drain metals. When the applied gate bias is higher than the threshold voltage, the high electron density channel with density of ~6 × 10¹⁷ cm^-3 and thickness of ~3-4 nm is observed near the interface of α-IGZO and gate dielectric. It results that the total gate capacitance is dominated by the gate to channel overlap. Quantitative analysis of the carrier distribution and energy band structures are utilized to study the physical mechanism underlying the C–V characteristics of the α-IGZO TFTs.

Abstract: We have fabricated Au/CuPc/Al/CuPc/Au organic thin film transistor (OTFTs) using vacuum deposition with CuPc thin films of stable chemical property and semi conductive Al gate thin film electrode. The static and dynamic characteristics were tested at room temperature. The test results show that the switching speed of the OTFT is t_on=2.68ms, t_off= 1.32ms, amplification bandwidth is 400Hz, and the cutoff frequency f_c=400Hz when inputting 100Hz small square wave signal. Our OTFT has submicron conductive channel, shows operation characteristics of high frequency, high speed and high current density. Good static and dynamic characteristics of OTFT can be obtained by controlling appropriate Al gate film thickness and CuPc film thickness.

Abstract: By using organic semiconductor CuPc as photosensitive materials, we prepared an organic thin film transistor with the vertical structure consisted of metal Cu/ organic semiconductor CuPc/ Al/ organic semiconductor CuPc/ indium tin oxide ITO. CuPc semiconductor material has good photosensitive properties in the 700 nm light. When the light signal irradiates organic semiconductor photosensitive material, the electron-hole exciton is separated into photocurrent in built-in electric field produced by organic semiconductor material/ metal schottky contact. It transforms into the driving current of organic photoelectric triode. By using its current amplification effect, the output current increase obviously. The test result shows that the I-V characteristics of the transistor are obvious unsaturated triode characteristics. When using 700 nm light to irradiate the device, the working current of the device increases obviously.