Electrical characteristics of single-gate interference transistors based on various semiconductor materials

The current-voltage and high-frequency characteristics of single-gate interference T transistors based on quantum wires made of various semiconductors, specifically, Si, Ge, GaAs, InAs, GaSb, InSb, GaP, and InP, were studied theoretically. Two scattering mechanisms were taken into account in the T-transistor model in order to assess their effect on the electrical characteristics of devices. The adequacy of the suggested model was verified by comparing the results of simulation with experimental data. The calculations were performed using the QW-NANODEV subsystem for simulating the devices based on quantum wires.     

不同偏置条件下PMOSFETs的剂量率效应研究

研究了不同剂量率、不同偏置条件下,PMOSFETs的辐照响应特性;并对高剂量率辐照后的器件进行了与低剂量率辐照等时的室温退火。结果表明,随着剂量率的降低,PMOSFETs阈值电压的漂移更加明显;不同偏置条件、不同剂量率范围内表现出TDE和ELDRS两种不同的剂量率效应。利用亚阈分离技术对影响阈值电压漂移的氧化物陷阱电荷和界面态进行了详细的机理分析,认为ELDRS效应的产生是由界面态密度的差异导致的。     

Dose-rate effects of p-channel metal oxide semiconductor field-effect transistors at various biasing conditions

The total-dose response and annealing effect of p-channel metal oxide semiconductor field-effect transistors (PMOSFETs) were investigated at various dose rates and biasing conditions.The results show that the shift of threshold voltage is more obvious when the dose rate is decreased.Under the various dose rates and biasing conditions,some have exhibited a time-dependent effect and others showed enhanced low-dose-rate sensitivity (ELDRS).Finally,using the subthreshold-separating method,the threshold-voltage shift is separated into shifts due to interface states and oxidetrapped charges,and the underlying mechanisms of the observed effects are discussed.It has been indicated that the ELDRS effect results from the different quantities of the interface states generated at high and low dose rates.     

Solution processable quinoxaline based molecular materials for organic field effect transistors

Three new solution processable quinoxaline based donor–acceptor–donor (D–A–D) type molecules have been synthesized for application in field effect transistors. These molecules were characterized by UV–visible spectroscopy, thermal gravimetric analysis, differential scanning calorimetry and cyclic voltammetry. DFT calculation gives deeper insight into the electronic structure of these molecules. The crystallinity and morphology features of thin film were investigated using X-ray diffraction. These molecules show liquid crystalline phase confirmed by DSC and optical polarizing microscopy. Investigation of their field effect transistor performance indicated that these molecules exhibited p-type mobility up to 9.7 × 10^?4 cm² V^?1 s^?1 and on/off ratio of 10⁴.     

Vertical structure permeable-base hybrid transistors based on multilayered metal base for stable electrical characteristics

In this work we present a permeable-base transistor consisting of a 60 nm thick N,N′-diphenyl-N,N′-bis(1-naphthylphenyl)-1,1′-biphenyl-4,4′-diamine layer or a 40 nm thick 2,6-diphenyl-indenofluorene layer as the emitter, a Ca/Al/Ca multilayer as the metal base, and p-Si as collector. In the base, the Ca layers are 5 nm thick and the Al layer was varied between 10 and 40 nm, the best results obtained with a 20 nm thick layer. The devices present common-base current gain with both organic layer and silicon acting as emitter, but there is only observable common-emitter current gain when the organic semiconductor acts as emitter. The obtained common-emitter current gain, ～2, is independent on collector-emitter voltage, base current and organic emitter in a reasonable wide interval. Air exposure or annealing of the base is necessary to achieve these characteristics, indicating that an oxide layer is beneficial to proper device operation.     

Effect of emitter contact materials on high-performance verticalp-n-p transistors

Ion-implant doped polysilicon, in situ doped polysilicon, and in situ doped ultrahigh vacuum chemical vapor deposition (UHV/CVD) low-temperature epitaxial silicon emitter contacts were used to fabricate shallow junction vertical p-n-p transistors. The effect of these materials on emitter junction depth and on device characteristics is reported. A DC current gain as high as 45 was measured on polysilicon emitter devices. Regardless of emitter contact material, all devices showed sufficiently high breakdown voltages for circuit applications. However, only for ion-implant doped polysilicon emitter devices was the narrow-emitter effect observed through the emitter-collector punchthrough voltage, emitter resistance, and current gain measurements     

Fully transparent flexible transistors built on metal oxide nanowires

Transparent electronics has attracted great research efforts in recent years due to its potential to make significant impact in many area, such as next generation displays, ultraviolet (UV) detectors, solar cells, charge-coupled devices (CCDs), and so on. Central to the realization of transparent electronics is the development of high performance fully transparent thin-film transistors (TFTs). One-dimensional (1-D) nanostructures have been the focus of current researches due to their unique physical properties and potential applications in nanoscale elec-tronics and optoelectronics. Among 1-D nanostructures, transparent metal oxide nanowires are one of the best candidates to make fully transparent TFTs. We provide in this paper the most recent development on the fabrication of fully transparent TFT using metal oxide nanowires as the device elements. First, the review article gives a general introduction about the development of transparent elec-tronics using different kinds of materials as the devices elements, including organic semiconductors, metal oxide thin films, and metal oxide nanowires. Second, the growth of metal oxide nanowires using vapor phase methods governed by two different growth mechanisms: vapor-solid mechanism and vapor-liquid-solid mechanism, respectively, are described. Third, the fabrication of transparent and flexible TFTs using different metal oxides nanowires is comprehensively described. In conclusion, the challenges and prospects for the future are discussed.     

Stabilizing contact resistance of isotropically conductive adhesives on various metal surfaces by incorporating sacrificial anode materials

The contact resistance stability of isotropically conductive adhesives (ICAs) on non-noble metal surfaces under the 85°C/85% relative humidity (RH) aging test was investigated. Previously, we demonstrated that galvanic corrosion has been shown as the main mechanism of the unstable contact resistance of ICAs on non-noble metal surfaces. A sacrificial anode was introduced into the ICA joint for cathodic protection. Zinc, chromium, and magnesium were employed in the ICA formulations as sacrificial anode materials that have much lower electrode-potential values than the metal pad surface, such as tin or tin-based alloys. The effect of particle sizes and loading levels of sacrificial anode materials were studied. Chromium was not as effective in suppressing corrosion as magnesium or zinc because of its strong tendency to self-passivate. The corrosion potential of ICAs was reduced by half with the addition of zinc and magnesium into the ICA formulation. The addition of zinc and magnesium was very effective in controlling galvanic corrosion that takes place in the ICA joints, resulting in stabilized contact resistance of ICAs on Sn, SnPb, and SnAgCu surfaces during the 85°C/85% RH aging test.     

Phase-insensitive all-optical transistors based on second-ordernonlinearities

We demonstrate and compare two phase-insensitive all-optical transistors (AOT's) based on frequency-degenerate quadratic three-wave interactions. In particular, we demonstrate gain using KTP in a type II geometry. Both AOT's exploit the phase insensitivity inherent to three-wave parametric processes when only two fields are input, providing amplification of a small signal at the operating frequency via the interaction with a second-harmonic wave. The first scheme is based on successive up- and down-conversion (i.e., cascading) while the second relies on parametric down-conversion. We obtain gains of 5 and 160 in the two configurations, respectively, with a significant background and output coherent to the pump in the first case, no background and coherence between output and signal in the second     

Frequency-output sensors-transducers based on unijunction transistors

The experimental characteristics of sensors of nonelectrical quantities (temperature, magnetic field, light, and pressure) based on a unijunction transistor (UJT), which is a component of a relaxation oscillator, have been investigated. Designs of measuring sensors-transducers in which the UJT and other circuit elements serve as components sensitive to external action are presented. It is shown that, if the output parameter of the sensors is the oscillation frequency that is determined by the magnitude of the corresponding action, insertion of additional sensing elements into the circuit makes it possible to significantly increase the efficiency of the sensors-transducers.     

Fabrication of gate-all-around transistors using metal inducedlateral crystallization

Gate-all-around transistor (GAT) is demonstrated. The device can be fabricated on either a bulk silicon wafer or on the top of any device layers. The fabrication process used a new technique called metal-induced-lateral-crystallization (MILC) to recrystallize amorphous silicon to form large silicon grains in the active area. Using this technique, the transistor performance is comparable to a SOI MOSFET. Compared with the single-gate thin film transistor (SGT) and solid phase crystallization (SPC) devices, the MILC GAT has lower subthreshold slope, lower threshold voltage, higher transconductance and nearly double drive current, The impact of short channel length was investigated     

Low-temperature materials and thin-film transistors for electronics on flexible substrates

The deposition processes and electronic properties of thin-film semiconductors and insulators based on silicon in relation to the fabrication of electronic devices on flexible plastic substrates are considered. The films of amorphous hydrogenated silicon (a-Si:H), nanocrystalline silicon (nc-Si), and amorphous silicon nitride (a-SiN_x), and also thin-film transistors are fabricated at comparatively low temperatures (120°C, 75°C) using existing commercial plasma-chemical equipment. The parameters of thin-film transistors based on a-Si:H and fabricated at the aforementioned relatively low temperatures are compatible with those of high-temperature analogues.     

激光对不同物质消融的研究

本文报道了用308nm XeCl激光消融聚合物及生物组织和角膜刻划的研究结果,并与1.06μm和0.53μm的纳秒、皮秒YAG激光消融生物组织的结果作了对比。     

Radiation sensitive detector based on field-effect transistors

The possibility of developing radiation detectors based on field-effect transistors (FET) is investigated. Transistor saturation current is chosen as an informative parameter for modeling. Experimental results show that the drain saturation current of the FET with p-n junction as a gate is decreasing after irradiation. In metal-oxide-semiconductor (MOS) FETs during radiation-induced defect formation two effects are competing, therefore the result of radiation influence is highly dependent on the electro-physical properties of transistors before irradiation and on the absorbed radiation dose. It is shown that saturation current increases with absorbed radiation dose for all the transistors with low electron concentration in a channel above certain levels of absorbed radiation. While the opposite effect is observed for high electron concentration in a channel, i.e. the saturation current drops. Obtained dependences of the drain saturation current of FET on the irradiation dose facilitated development of simple detector design for low levels of radiation. The bridge circuit is used in the radiation sensor to minimize the effect of temperature fluctuations. The sensitivity of the detector is enhanced several times with the help of two pairs of FETs with the opposite sign of radiation sensitivity.     

Ultrawide-band gigahertz-range transceiver based on SiGe transistors

The aspects of designing an integrated circuit of a transmitter based on SiGe heterojunction transistors are considered. The circuit feature is the application of fast analog-to-digital converters and also unconventional phase-locked loop circuitry with low phase noise. A device for radio transmission with a rate of 1.35 Gbit/s is numerically simulated and experimentally studied. The experimental results are in good agreement with simulation data.     

基于聚合物电介质的并五苯场效应晶体管

采用顶接触结构分别在SiO2、聚甲基丙烯酸甲酯(PMMA)绝缘层上制备了以并五苯为有源层的两种有机场效应晶体管(OFET),其中SiO2绝缘层采用热生长法制备,PMMA绝缘层采用溶液旋涂法制备。与常规基于无机绝缘层的器件相比,采用聚合物为绝缘层后,不但器件的制作工艺简化和成本降低,而且器件性能大幅提高,经测试,器件的迁移率提到0.153cm2/Vs,而阈值电压降低6V。采用原子力显微镜(AFM)、X射线衍射(XRD)等对器件性能提高的原因进行了详细分析。     

Analog-to-digital converter based on single-electron tunneling transistors

A novel single-electron tunneling transistors (SETTs) based analog-to-digital converter (ADC) is proposed in this paper. The scheme we propose fully utilizes Coulomb oscillation effect, can properly operate at T>0 K, and only a capacitive divider (built with 2n-2 capacitors) and n pairs of complementary SETTs are required for an n-bit ADC implementation. When compared with other state-of-the-art SET based ADCs our method provides the most compact solution measured in terms of circuit elements and has a potential advantage in terms of conversion speed. To illustrate the operation of the proposed scheme, a 4-bit ADC is demonstrated at 10K by means of simulation.     

Microwave field-effect transistors based on group-III nitrides

A concept for the design of experimental AlGaN/GaN/AlGaN double heterostructures with a two-dimensional electron channel are discussed, together with their main properties. The structures were formed by ammonia molecular-beam epitaxy on sapphire substrates. The foundations for postgrowth technology are developed for microwave field-effect transistors based on Group-III nitrides, including the formation of a mesa isolation and the preparation stage of nonrectifying contacts and the Schottky barrier. The first field-effect transistors fabricated based on the above heterostructures have a complete set of static characteristics and can operate in a mode of weak microwave signals at a frequency of 8.15 GHz.     

Ambipolar organic transistors based on isoindigo derivatives

Structural and transistor properties of isoindigo derivatives are investigated. The unsubstituted isoindigo affords two polymorphs in addition to the reported brickwork structure; one has a stacking structure analogous to indigo, and another consists of nonplanar molecules. The unsubstituted isoindigo exhibits ambipolar transistor properties with the hole and electron mobilities more than 0.01 cm²/Vs, and 6.6′-diphenylisoindigo shows ambipolar transistor properties with the hole/electron mobilities of 0.037/0.027 cm²/Vs. Isoindigo derivatives with electron withdrawing groups show only electron transport, indicating that the lower limit of the HOMO level showing the hole transport is −5.7 eV.     

Parameters calculation of drift n-p-n transistors using their output characteristics

A methodology of estimating physical parameters of transistor’s structure in order to obtain the necessary set of its main electrical parameters is described. The suggested methodology is based on applying semi-empiric formulas, obtained by means of statistical processing of a large number of experimental data, and allows determining parameters of transistor’s structure with the best optimal combination of current gain, breakdown voltage and cutoff frequency. The methodology is proven by numerous experimental results.