High gamma dose induced damage on two types of discrete JFET transistors

The effect of high Gamma ray dose on two types of commercial transistors having different DC specifications has been investigated. The transistors were discrete N-JFETs intended as front-end component in nuclear read-out systems. They were exposed to different Gamma doses with a maximum of 10,000 kGy. The irradiation influence was represented by the analysis of the DC and the induced noise characteristics.The results show that the noise was more sensitive to irradiation than the DC parameters, and the radiation effect depends on the original DC specifications. It was also found that the first dose induces noise more than the next doses. Similar effects were observed either if the irradiation is done by one single dose or by many successive accumulated doses.     

Effect of Microwave Radiation on Quantum Magnetocapacitance Oscillations

JETP Letters - The effect of microwave radiation on the amplitudes of the quantum magnetocapacitance oscillations in field-effect transistors has been studied. It has been found that the...     

Suppression of the tunneling effect by shallow junctions in field-effect transistor

We study the quantum wave transport in nanoscale field-effect transistors. It has been shown that the tunneling effect between the source and the drain in an ultra-short channel transistor significantly degrades the control of the drain current by the gate. However, the tunneling effect is suppressed by reducing the depth of the source and drain junctions which is designated to suppress the short-channel effects concerning the cut-off characteristics of the field-effect transistor. The reduced junction depth confines the carriers in the direction (y -direction) perpendicular to the transport direction (x -direction). The matching of y -direction wavefunctions at regional boundaries suppresses the tunneling effect and normal FET current–voltage characteristics has been obtained, which explains theoretically the successful fabrication of nanoscale field-effect transistors.     

Influence of different type irradiation on the parameters of silicon semiconductor devices

Effect of different irradiation (by electrons, neutrons, protons, and gamma) on the main properties of silicon-based semiconductor devices has been studied. A higher emphasis has been placed on transistors as the least radiation-stable structures. It is shown that under irradiation by protons the modification of corresponding parameters occurs at relatively lower doses. The results are explained on the basis of arising of surface channels of conductivity under irradiation.     

The Spectrum of Deep Levels in the InP Schottky Barrier

The energy spectrum of deep levels in the space-charge region of the Schottky barrier of InP field-effect transistors is determined by the method of tunneling spectroscopy. It has been established that for the most part the space-charge region of the Schottky barrier has electron traps with large capture cross sections that control the tunneling current in the Schottky barrier.     

Effect of interfacial shallow traps on polaron transport at the surface of organic semiconductors

The photo-induced electron and hole transfer across the semiconductor-dielectric interface in trap-dominated p-type organic field-effect transistors has been investigated. It has been observed that the transfer of electrons into the dielectric results in a decrease of the field-effect mobility of polarons, suggesting that additional shallow traps are generated in the conduction channel. Using this effect, the dependence of the field-effect mobility on the density of shallow traps, mu(N), has been measured, which allowed us to estimate the average polaron trapping time, tau_{tr}=50+/-10 ps, and the density of shallow traps, N0=(3+/-0.5) x 10(11) cm(-2), in the channel of single-crystal tetracene devices.     

Noise sensitivity to gamma radiation in Si-jfet devices

The result of noise measurements for a Charge Sensitive Preamplifier based on Si-Field Effect Transistor exposed to a total Gamma ray dose of 30 v Mrad have been reported. The radiation effect on the DC parameters of single transistors was also tested. Our study has shown that, there are no changes on the DC parameters. Meanwhile the noise level, which was evaluated by the total equivalent noise charge, was clearly increased. The results of noise measurements were analyzed and compared with theoretical predictions. The temperature and time-dependent effects on the noise had also been reported after irradiation. All measurements were performed for biased and unbiased irradiated transistors.     

Electrical and optical properties of light-emitting field-effect transistors based on MEH-PPV polymer composite films with ZnO nanoparticles

The optical and electrical properties of light-emitting field-effect transistor structures with an active layer based on nanocomposite films containing zinc oxide (ZnO) nanoparticles dispersed in the matrix of the soluble conjugated polymer MEH-PPV have been investigated. It has been found that the current-voltage characteristics of the field-effect transistor based on MEH-PPV: ZnO films with a composite component ratio of 2: 1 have an ambipolar character, and the mobilities of electrons and holes in these structures at a temperature of 300 K reach high values up to ～1.2 and ～1.4 cm²/V s, respectively, which are close to the mobilities in fieldeffect transistors based on ZnO films. It has been shown that the ambipolar field-effect transistor based on MEH-PPV: ZnO films emits light at both positive and negative gate bias voltages. The mechanisms of injection, charge carrier transport, and radiative recombination in the studied structures have been discussed.     

Comparison between post-irradiation annealing and post-high electric field stress annealing of n-channel power VDMOSFETs

The behavior of the defects created in the gate oxide and at the Si/SiO₂ interface of n-channel power vertical double-diffused metal-oxide-semiconductor field-effect transistors (VDMOSFETs) by irradiation and positive high electric field stress have been investigated. Interface traps exhibit the same behavior after both types of stress, while there are significant differences in post-stress responses of the charge trapped in the oxide, consisting of fixed and switching component.     

Bias dependence of a deep submicron NMOSFET response to total dose irradiation

Deep submicron n-channel metal-oxide-semiconductor field-effect transistors (NMOSFETs) with shallow trench isolation (STI) are exposed to ionizing dose radiation under different bias conditions.The total ionizing dose radiation induced subthreshold leakage current increase and the hump effect under four different irradiation bias conditions including the worst case (ON bias) for the transistors are discussed.The high electric fields at the corners are partly responsible for the subthreshold hump effect.Charge trapped in the isolation oxide,particularly at the Si/SiO 2 interface along the sidewalls of the trench oxide creates a leakage path,which becomes a dominant contributor to the offstate drain-to-source leakage current in the NMOSFET.Non-uniform charge distribution is introduced into a threedimensional (3D) simulation.Good agreement between experimental and simulation results is demonstrated.We find that the electric field distribution along with the STI sidewall is important for the radiation effect under different bias conditions.     

Bias Dependence of Radiation-Induced Narrow-Width Channel Effects in 65 nm NMOSFETs

The bias dependence of radiation-induced narrow-width channel effects(RINCEs) in 65-nm n-type metal-oxidesemiconductor field-effect transistors(NMOSFETs) is investigated. The threshold voltage of the narrow-width65 nm NMOSFET is negatively shifted by total ionizing dose irradiation, due to the RINCE. The experimental results show that the 65 nm narrow-channel NMOSFET has a larger threshold shift when the gate terminal is kept in the ground, which is contrary to the conclusion obtained in the old generation devices. Depending on the three-dimensional simulation, we conclude that electric field distribution alteration caused by shallow trench isolation scaling is responsible for the anomalous RINCE bias dependence in 65 nm technology.     

Nyquist noise of cell adhesion detected in a neuron-silicon transistor

Interfacing of nerve cells and field-effect transistors is determined by current flow along the electrical resistance of the cell-chip junction. We study the thermal noise of the junction by measuring the fluctuations of extracellular voltage with a low-noise transistor. We find a spectral power density of 5 x 10(-14) V2/Hz and interpret it as Nyquist noise of the cell-chip junction with a resistance of 3 MOhm. The thermal noise allows us to elucidate the properties of cell adhesion and it sets a thermodynamical limit for the signal-to-noise ratio of neuroelectronic interfacing.     

Research on total-dose hardening for H-gate PD NMOSFET/SIMOX by ion implanting into buried oxide

In this work,we investigate the back-gate I-V characteristics for two kinds of NMOSFET/SIMOX transistors with H gate structure fabricated on two different SOI wafers.A transistors are made on the wafer implanted with Si+ and then annealed in N2,and B transistors are made on the wafer without implantation and annealing.It is demonstrated experimentally that A transistors have much less back-gate threshold voltage shift AVth than B transistors under X-ray total dose irradiation.Subthreshold charge separation technique is employed to estimate the build-up of oxide charge and interface traps during irradiation,showing that the reduced △Vth for A transistors is mainly due to its less build-up of oxide charge than B transistors.Photoluminescence (PL) research indicates that Si implantation results in the formation of silicon nanocrystalline (nanocluster) whose size increases with the implant dose.This structure can trap electrons to compensate the positive charge build-up in the buried oxide during irradiation,and thus reduce the threshold voltage negative shift.     

Memory element based on ferroelectric field-effect transistor with use of ZnO:Li/LaB6 heterostructures

Ferroelectric field-effect transistors using ZnO:Li films simultaneously as a transistor channel and as a ferroelectric active element have been prepared and studied. We show an opportunity of using the ferroelectric field-effect transistor based on ZnO:Li films in ZnO:Li/LaB₆ heterostructure as a bistable memory element for information recording. The proposed structure of a ferroelectric memory cell does not possess the fatigue under repeated readout of single recorded information that will allow increasing the resource of storage devices essentially.     

Interaction effects in conductivity of Si inversion layers at intermediate temperatures

We compare the temperature dependence of resistivity rho(T) of Si-metal-oxide-semiconductor field-effect transistors with the recent theory by Zala et al. In this comparison, the effective mass m* and g* factor for mobile electrons have been determined from independent measurements. An anomalous increase of rho with temperature, which has been considered as a signature of the "metallic" state, can be described quantitatively by the interaction effects in the ballistic regime. The in-plane magnetoresistance rho(B(axially)) is only qualitatively consistent with the theory; the lack of quantitative agreement indicates that the magnetoresistance is more sensitive to sample-specific effects than rho(T).     

Organic field-effect transistors

The paper reviews the recent year publications concerning organic field-effect transistors (OFETs). A lot of works have been performed to help understanding the structural and electrical properties of materials used to construct OFETs. It has been established that in partially ordered systems, the charge transport mechanism is thermally activated and field-assisted hopping transport and the hopping transport between disorder-induced localized states dominate over intrinsic polaronic hopping transport seen in organic single crystals. Many research attempts have been carried out on the design of air-stable organic semiconductors with a solution process which is capable of producing OFETs with excellent properties and good stability when subjected to multiple testing cycles and under continuous electrical bias. Recent experiments have demonstrated ambipolar channel conduction and light emission in conjugated polymer FETs. These achievements are the basis for construction of OLED based displays driven by active matrix consisting of OFETs.     

Patterning graphene nanostripes in substrate-supported functionalized graphene: A promising route to integrated, robust, and superior transistors

It is promising to apply quantum-mechanically confined graphene systems in field-effect transistors. High stability, superior performance, and large-scale integration are the main challenges facing the practical application of graphene transistors. Our understandings of the adatom-graphene interaction combined with recent progress in the nanofabrication technology indicate that very stable and high-quality graphene nanostripes could be integrated in substrate-supported functionalized (hydrogenated or fluorinated) graphene using electron-beam lithography. We also propose that parallelizing a couple of graphene nanostripes in a transistor should be preferred for practical application, which is also very useful for transistors based on graphene nanoribbon.     

Meyer–Neldel rule in fullerene field-effect transistors

The temperature dependence of the field-effect mobility is investigated in vacuum evaporated C₆₀-based organic field-effect transistors. The results show a thermally activated behavior with an activation energy that depends on the field-induced charge carrier density in the transistor channel. Upon extrapolation of the data in an Arrhenius plot we find an empirical relation, termed the Meyer–Neldel rule, which states that the mobility prefactor increases exponentially with the activation energy. Based on this analysis a characteristic temperature is extracted. The possible implications of this observation in terms of charge transport in fullerene-based field-effect transistors are discussed.     

Type of the second hole subband on the Si(110) surface: Spin splitting anisotropy

Magnetoresistance measurements have been performed for the cases of one and two occupied size-quantization hole subbands in silicon field-effect transistors prepared on the Si (110) surface. In both cases, Shubnikov-de Haas oscillations exhibit very weak sensitivity to the in-plane component of the magnetic field. This indicates that both lowest subbands are formed by heavy holes. This conclusion disagrees with the wide-spread opinion that the second subband is the ground subband of light holes in the system under consideration.     

Influence of surface processing in a BCl<Subscript>3</Subscript> plasma on the formation of ohmic contacts to AlGaN/GaN structures

Conditions for the surface processing of a cap GaN layer in AlGaN/GaN high-electron-mobility transistor (HEMT) structures in a BCl₃ plasma have been found. They make it possible to considerably reduce the resistance of ohmic contacts to Group III nitride-based field-effect transistors. The primary factor behind this effect is the noticeable lowering of a potential barrier on the GaN surface through the formation of nitrogen vacancies that act as donors and, correspondingly, a rise in the surface concentration of electrons.