Radiation-hardened silicon-on-insulator complementary junction field-effect transistors

The effects of total-dose radiation have been investigated for complementary junction field-effect transistors fabricated in zone-melting recrystallized Si films on SiO2-coated Si substrates. With a - 5-V bias applied to the Si substrate during irradiation and device operation, both n- and p-channel devices show low threshold-voltage shift (<-0.09 and <-0.12 V, respectively), low leakage currents (<- 1- and <3-pA/µm channel width, respectively) and small transconductance degradation (<15 percent) for total doses up to 10⁸rad (Si).     

Radiation-hardened silicon-on-insulator junction field-effect transistors fabricated by a self-aligned process

A self-aligned process has been developed for fabricating JFET's in zone-melting-recrystallized (ZMR) Si films on SiO2-coated Si substrates. This process has been used to fabricate n-JFET's exhibiting transconductance values up to 63 mS/mm. For 228 devices within an area of about 4 × 4 cm², the mean threshold voltage is 578 mV and the standard deviation is 22 mV. With a -15-V bias applied to the Si substrate during irradiation and device operation, the devices show low threshold voltage shift (< -75 mV) and small transconductance degradation (∼30 percent) for exposure to total-dose radiation of 10⁸rad(Si).     

Output characteristics of short-channel field-effect transistors

A recent model for hot-electron MOS transistors [4], [5] is generalized for short-channel field-effect transistors. It is based on six to seven parameters for the carrier mobility under the influence of transverse and Iongitudinal electric fields, for the threshold voltage and its dependence on drain bias, and for a finite longitudinal field at pinch-off. Such important features of short-channel FET's like reduced available current and voltage gain are well represented, where the latter turns up as important limiting factor in submicron devices. Effects of zero-field mobility, impurities, and device geometry are stated explicitly. The results are confirmed by measured data on 0.9-µm silicon gate MOSFET's.     

Device characteristics of polymer dual-gate field-effect transistors

Dual-gate organic field-effect transistors (OFETs) were fabricated by solution processing using different p-type polymer semiconductors and polymer top-dielectric materials on prefabricated substrates with gold source-drain contacts defined by photolithography. The semiconductors and top dielectrics films were processed from solution by spin-coating and the silver top gate was applied by shadow mask evaporation. The dual-gate OFETs were characterized in double gate mode by sweeping the bottom gate bias from 40 to −50 V while fixing the top gate potentials, and vice versa. We demonstrate that the change in the threshold voltage of the bottom gate depends on the top gate bias with two linear relationships for two different regimes. The interpretations of the results, assuming that the mobilities of the top and bottom channels have similar magnitudes, and that the capacitance of the semiconductor layer is not negligible, indicated two distinct regimes for a dual-gate p-type OFET.1. When one gate is positive, hence the respective channel is in depletion and no gate screening will occur, while the other gate is in accumulation regime, the field of the positive gate will penetrate to such a large extend that the channel in accumulation will be affected by both gates.2. When both channels are in accumulation, the charges present in the channels will screen the respective gate potentials, hence both channels will operate individually and no mutual influences are observed.For a dual-gate OFET with its top channel in accumulation, we demonstrate a drop in the transconductance when the bottom gate potential becomes negative. This transition regime between both linear regimes is marked by a drop in the transconductance, where the bottom channel depends on the bottom gate only and the top channel will depend on both gates. The transition regime results from the fact that the charges accumulated in the bottom channel will start to screen the influence of the bottom gate potential on the top channel and the change in overall drain current will depend only on the change of the current of the bottom channel.     

Noise characteristics of gallium arsenide field-effect transistors

Small signal and noise characteristics for GaAs field-effect transistors are derived with the saturated drift velocity of the carriers underneath the gate taken into account. The noise contributed by the saturated carriers is nonnegligible and in most cases, exceeds the noise generated by the unsaturated region. Parasitic elements contribute importantly by preventing the full cancellation of the correlated noise of the intrinsic transistor and by adding their own Johnson noise. The theory predicts the experimentally observed trend of noise figure dependence on drain current and on source-to-drain voltage. The present theory doesnot take into account the effects of a possible short negative resistance region underneath the gate.     

关于短沟道双栅无结型晶体管的仿真研究

We study the characteristics of short channel double-gate(DG) junctionless(JL) FETs by device simulation. OutputⅠ-Ⅴcharacteristic degradations such as an extremely reduced channel length induced subthreshold slope increase and the threshold voltage shift due to variations of body doping and channel length have been systematically analyzed.Distributions of electron concentration,electric field and potential in the body channel region are also analyzed.Comparisons with conventional inversion-mode(IM) FETs,which can demonstrate the advantages of JL FETs,have also been performed.     

ANALYTICAL RESEARCH ON THE STATIC CHARACTERISTICS OF HETEROSTRUCTURE ISOLATED GATE FIELD-EFFECT TRANSISTORS

Based on improved charge control model and combining GSW velocity-field equa-tion, a series of analytical solutions for the static characteristics of HIGFETs such as I_D-V_D-V_G,I_(DS)-V_G, G_m and C_G are derived. The results of calculation are compared with experimentaldata reported in references, within the range of V_G<2V, I_D相似文献   

ZnO纳米线场效应管的制备及光电特性

本文采用水热法生长的ZnO纳米线制得悬浮ZnO纳米线场效应晶体管,该场效应管的跨导为0.396μS,迁移率为50.17cm^2/Vs,VGS = 0 V时电阻率为0.96×102Ωcm,开关态电流比（Ion/Ioff）为10^5。该效应管在紫外下曝光（2.5μw/cm2）后显示了穿通现象和开启电压漂移（从-0.6V 到 +0.7V）,且由于漏极感应势垒的降低,使得源漏电流减少一半（从560nA到320nA）。悬浮ZnO纳米线场效应管的这些性质揭示了它的一些内在属性和器件方面的应用。     

Fabrication and photoelectrical characteristics of ZnO nanowire field-effect transistors

rease by almost half of the source-drain current (Ids, from 560 nA to 320 nA) due to drain-induced barrier lowering.Continued work is underway to reveal the intrinsic properties of suspended ZnO nanowires and to explore their device applications.     

CW oscillation characteristics of GaAs Schottky-barrier gate field-effect transistors

The CW oscillation characteristics of GaAs Schottky-barrier gate FET's have been examined at 10 GHz. The maximum output power of 41.2 mW and the maximum efficiency of 15.6 percent have been obtained for the GaAs FET with a gate length of 1.5 µm and an electrode width of 300 µm. The experimental results have shown that the GaAs FET possesses promising features for an oscillator application as well as an amplifier application.     

Influence of impact ionization on the drain conductance inInAs-AlSb quantum well heterostructure field-effect transistors

Using an InAs-AlSb heterostructure field-effect transistor (HFT) structure modified to incorporate an epitaxial p-type GaSb back gate, we measure the impact ionization current caused by hot electrons in the InAs channel. We show that the impact ionization current is only a small fraction of the deleterious increase in the drain current commonly observed in InAs-based transistors. Most of the drain current rise is caused by a feedback mechanism in which holes escaping into the substrate act like a positively charged parasitic back gate leading to an increase in the electron current flow in the channel by an amount that is large compared to the impact ionization current itself. Removal of the impact-generated holes by the epitaxial back gate breaks the feedback loop, and dramatically improves the DC characteristics of the devices, and increases the range of usable drain voltages     

Low-frequency noise characteristics of AlInAs/GaInAs modulation-doped field-effect transistors

The output noise voltage of AlInAs/GaInAs MODFETs grown by both MOCVD and MBE was measured at frequencies from 1 MHz to 1.5 GHz under different bias conditions for the first time. For frequencies below 500 MHz the noise voltage showed a 1/f dependence with a corner frequency around 200 MHz. The low-frequency noise was larger at the bias conditions giving higher transconductance.<>     

Applications of resonant-tunneling field-effect transistors

Flip-flop and frequency-doubling operations are demonstrated, using a simple circuit that combines a resistor with a three-terminal negative-resistance device. The device is a series integration of resonant-tunneling heterostructure with a field-effect transistors. Results, obtained at 77 K, are presented for two samples that were grown by metalorganic chemical vapor deposition     

Computation of mixing coefficients for field-effect transistors with non-square-law transfer characteristics

A recursive relationship is developed for the computation of coefficients in the polynomial approximation to an f.e.t. transfer characteristic. The analysis is valid for any value of resistance in the source circuit and takes account of practical departures from the idealised square-law relationship which is frequently assumed to represent the device.     

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.     

Gate-voltage-dependent transport measurements on heterostructure field-effect transistors

Heterostructure field-effect transistors (HFET's) with a quasi-two-dimensional electron gas as a channel need further optimization with respect to transport properties such as mobility, velocity, and carrier concentration and confinement. For the control of optimization procedures, analytical test methods are required. One suitable method is described here. It is an extension of the magnetotran-sconductance mobility measurement method [9] and allows a detailed analysis of transconductance, mobility, and sheet carrier concentration in the quasi-two-dimensional channel as a function of gate bias. The theory is described and experimental results on double (quantum well) heterojunction FET's are given. The assumption that parallel Conduction in HFET's at 77 K and at room temperature has different reasons [1], [2] will be proved experimentally. The great advantage of this method is its applicability to fully processed short-channel devices; its limitation is the restriction to the low-field constant-mobility regime.     

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.