Determination of Base Spreading Resistance and Junction Temperature of Uniform-base Junction Transistors†

The propagation of waves in incompressible beam-plasma systems is investigated on the basis of linear fluid equations. The pressure is assumed scalar and the incompressibility condition is chosen to illustrate a class of non-barotropic plasmas. The dispersion law For these linear waves is derived, and is generally discussed. The case of oblique propagation differs appreciably from results obtained for barotropic plasmas, mainly because compressional longitudinal waves are absent. Alfvén. waves in beam-plasma systems are then denned as low-frequency waves, with wave and drift frequencies small compared to gyrofrequencies. The Alfvén approximation of the dispersion law shows that the wave frequency at fixed wave-number is lower than if no streaming were applied.     

Theory of the Double Probe at High Gas Pressure†

It is shown that the mean electron energy in a uniform steady plasma at high gas pressure can be obtained from the analysis of a plane double probe curve. If the motion of charges to the boundary is controlled by diffusion and mobility, their production by single electron collisions and their loss by charge neutralization on the wall, the electron temperature is found from a relation which is similar to that for probes at low pressure. The mechanism of selection of electrons of different energy by a probe at low gas pressure is contrasted with that at high pressure and the application of the theory to various physical systems is discussed.     

Reliability Investigation of 0.18-μm SOI MOS Transistors at High Temperatures

In this paper, we estimate the basic parameters of 0.18-μm SOI MOS transistors in the temperature range from –60 to 300°С and investigate their reliability at high temperatures. The specific characteristics of SOI MOS transistors that manifest themselves at high temperatures should be taken into account when designing high-temperature integrated circuits in order to avoid their premature failures and improve the reliability of electronic devices.     

Boundary Conditions at a Plasma Junction with Drift Current†

Using a, spherieal Langinuir probe, it has been found that a boundary condition between the Faraday dark space and the head of n striated positive column in a number of discharges through neon is approximate equality of drift and random currents. It is possible that this may be a general condition at the junction of two plasmns traversed by drift current.     

1200 V 4H-SiC Bipolar Junction Transistors with A Record β of 70

A common current gain of 70 has been achieved in 4H-SiC bipolar junction transistors (BJTs) at room temperature, which is the highest among those reported. BJTs having an active area of 4 mm × 4 mm exhibit a specific on-resistance of 6.3 mΩ cm² at 25°C, which increases to 17.4 mΩ cm² at 250°C. BV_CEO (the breakdown voltage from collector to emitter with open base) and BV_CBO (the breakdown voltage from collector to base with open emitter) of 1200 V were observed at <5 μA leakage currents at all temperatures up to 250°C. Dynamic characteristics were measured using the IXYS RF/Directed Energy IXDD415 gate driver evaluation board to drive the BJT. A collector current (I _C) rise time at turn-on of 32 ns was measured with a 1.6 A gate current provided to support the collector current of 63 A. An I _C fall time at turn-off of 16 ns was achieved.     

Frequency Variations of π-equivalent Circuit Parameters of a Junction Transistor †

One of the most useful small-signal equivalent circuit representations is based on a m-equivalent circuit representation of the transistor in a common-emitter connection. This m-equivalent circuit representation is more readily and commonly employed in circuit analysis or design in comparison with a ^'-equivalent circuit representation. The variation of equivalent circuit parameters at high frequencies in the π-equivalent circuit representation was determined by Giacoletto experimentally. Unfortunately, however, we have no example but the above, in spite of this problem being very common and important. The exact expression for π-equivalent circuit parameters is too complicated to be calculated. The result may be somewhat simplified by expanding the hyperbolic function into a Taylor series and retaining only the first few terms. Numerical values of these approximate expressions are calculated and then compared with values calculated from the corresponding exact expression. Furthermore, w-equivalent circuit parameters relative to low-frequency values are given as a function of frequency relative to f_T and f_α. The π-equivalent circuit parameters of a p-n-p germanium alloy-junction transistor of the diffusion (homogeneous base) type are obtained by measuring small-signal h parameters under the low-level injection conditions with an impedance bridge. Then, it is made clear that they are in reasonably good agreement with theoretical values. The approximate expression for α is proposed, where α is analysed in terms of magnitude and phase shift. It is shown that it is more exact and more useful than the expressions such as the Thomas-Moll expression, etc., as a result of discussing the errors in the approximations of the equations.     

Development of gyrotrons at Thomson-CSF†

In this paper, experimental results on a 35 GHz 250 kw gyrotron oscillator (TH 1501 A) are first summarized. The project of a 70 GHz oscillator operating on the second harmonic of the cyclotron resonance is then discussed, and first experimental results are described. Theoretical work on space charge effects in a single orbit cylindrical beam oscillator is also reported. Numerical results indicate typically a 15% decrease in logarithmic gain.     

The Growth of Pre-breakdown Currents in a Uniform Electric Field Gap†

The pre-breakdown current across a uniform electric field gap has been calculated in the presence of ionization by electron impact and secondary electron processes. The solution improves upon the Townsend equation (1915) by allowing for the loss of secondary electron current out of the discharge gap. By using the published results of other workers, it has been shown that pre-breakdown currents, measured in the presence of losses, have fitted both the proposed solution and the Townsend equation but for different values of the electron ionization coefficient and the secondary electron coefficient (denoted by α and γ, and α _T and γ _T respectively). For all gases α_T ≥ α and γ _T ≤ γ and the inequality existed for all E/p values when photon secondary processes were active. The largest disagreement (α _T / α = 1 → 1 and γ / _T = 20 → 1) was calculated for argon for E/ < v cm^?1 torr^?1.     

High–Bias–Field Operation of GaAs Photoconductive Terahertz Emitters

Journal of Infrared, Millimeter, and Terahertz Waves - We demonstrate experimentally the increase of optical-to-terahertz conversion efficiency for GaAs-based photoconductive terahertz emitters....     

AlGaN/GaN High Electron Mobility Transistors on Sapphires with fmax of 100GHz

制作了蓝宝石衬底上生长的AlGaN/GaN高电子迁移率晶体管.0V栅压下,0.3μm栅长、100μm栅宽的器件的饱和漏电流密度为0.85A/mm,峰值跨导为225mS/mm;特征频率和最高振荡频率分别为45和100GHz;4GHz频率下输出功率密度和增益分别为1.8W/mm和9.5dB,8GHz频率下输出功率密度和增益分别为1.12W/mm和11.5dB.     

Study on Photocapacitance in PN Junction of High Resistivity P—type Silicon

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Dielectric Properties of Yttria Ceramics at High Temperature

Based on Clausius-Mosotti equation and Debye relaxation theory, the dielectric model of yttria ceramics was developed according to the dielectric loss mechanism. The dielectric properties of yttria ceramics were predicted at high temperature. The temperature dependence and frequency dependence of dielectric constant and dielectric loss were discussed, respectively. As the result, the data calculated by theoretical dielectric model are in agreement with experimental data.     

On the Stabilization of an Electron Bombardment Ion Source for a Mass Spectrograph Applying Power Transistors†

Power transistors are applied for the stabilization of the omission current of an electron bombardment ion source for a mass spectrograph.

The stabilizer is investigated by methods of servomechanism in order to examine the degree of stability.

Applying this stabilizer for Mattauch-Horzog Mass Spectrograph, Max Planck Institut, Mainz, Western Germany, the following stability for the electron current (i) is obtained:

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by a 10% change in the input voltage.

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by a 20% change in the accelerating voltage.     

Electrical Conductivity of Parylene F at High Temperature

The electrical conductivity of both as-deposited and annealed poly(α,α,α′,α′-tetrafluoro-p-xylylene) (PA-F) films has been investigated up to 400°C. The static conductivity (σ _DC) values of PA-F measured between 200°C and 340°C appear to be ∼2.5 orders of magnitude lower for annealed films than for as-deposited ones. This change is attributed to a strong increase in the crystallinity of the material occurring above 340°C. After annealing at 400°C in N₂, the σ _DC value measured at 300°C, for instance, decreased from 3.8 × 10⁻¹² Ω⁻¹ cm⁻¹ to 7.5 × 10⁻¹⁵ Ω⁻¹ cm⁻¹. Physical interpretations of such an improvement are offered.     

Studies on Dielectric Properties of Silicon Nitride at High Temperature

In this paper, the dielectric properties of silicon nitride are studied using the dielectric polarization theories. According to the developed dielectric models, the temperature dependence of dielectric constant and loss of silicon nitride is mainly analyzed. In addition, the impact of Li^＋, K^＋, Ca^2＋, Al^3＋ and Mg^2＋ doping on the dielectric properties of silicon nitride are also estimated.     

The Electron Temperature of the Positive Column in Hydrogen at Low Pressure†

Excitation of slow electromagnetic waves in a waveguide filled with magnetized plasma, using a ring of magnetic current placed along a gap in the waveguide wall, is analysed. It is pointed out that coupling of the electromagnetic power may be enhanced by a localized increase of plasma density near the coupler.     

S-Shaped I–V Characteristics of High-Power Schottky Diodes at High Current Densities

Semiconductors - The effect of a set of quasi-neutral regimes of carrier transport in semiconductors, including, along with diffusion and drift, recently discovered diffusion stimulated by...     

High Performance β-Ga2O3 Schottky Barrier Transistors with Large Work Function TMD Gate of NbS2 and TaS2

Gallium trioxide, β-Ga₂O₃, has been recently studied due to its promising semiconducting properties as active material in transistors or Schottky diodes. Transistors with β-Ga₂O₃ channels are mostly metal oxide field effect transistors (MOSFET), and they show very negative threshold voltages (V_th) in general. Metal semiconductor field effect transistors (MESFETs) with top gate are also reported with less negative V_th. Still, β-Ga₂O₃ MESFETs are only a few. Here, bottom gate architecture β-Ga₂O₃ MESFETs using transition metal dichalcogenide (TMD) NbS₂ and TaS₂ are reported. Due to the large work functions of those metallic TMDs, the MESFETs display minimum subthreshold swing of 61 mV dec⁻¹, small V_th of −1.2 V, minimum OFF I_D of ≈100 fA, and maximum ON/OFF current ratio of ≈10⁸. Both β-Ga₂O₃ Schottky diodes with TaS₂ and NbS₂ display good junction stability even after 300 °C measurements in 10 mTorr vacuum. When the β-Ga₂O₃ MESFET with TaS₂ gate is integrated as a switching FET into an organic light emitting diode (OLED) circuit, it demonstrates long-term leakage endurance performance, maintaining an OLED brightness higher than 58% of the initial intensity after 100 s passes since the ON-switching point, which is even superior to the performance of conventional a-IGZO MOSFET switch.     

Dielectric strength and interface-state behaviour of oxygen plasma-grown SiO2 films annealed at high temperature†

The behaviour of the interface-state density in plasma oxidized silicon dioxide on silicon MOS structures has been investigated as a function of annealing temperature and time for anneals in an ambient of dry nitrogen. It was found that the interface-state density decreases with increasing annealing time and temperature, saturating at a temperature of approximately 950^°C and a time of approximately one hour.

In situ r.f. sputter-cleaning prior to oxidation produces dielectric films of uniformly high and reproducible dielectric strength of up to 10⁷ volts/em, in contrast to most chemical cleaning processes which typically yield lower dielectric strengths and greater variability.     

Behaviour of Ti Based on Si （111） Substrate at High Temperature in Oxygen

The behavior of Ti based on Si（lll） in oxygen under high temperatures（700 ℃, 800 ℃ , 900 ℃ , I 000 ℃ and 1 100℃） is reported. X-ray diffraction（XRD） and Fourier transform infrared spectroscopy （FTIR） are used to analyze the structure and composition of the samples annealing at different temperatures in oxygen ambience. It is found that raising temperature is helpful to the formation of both TiSi2 and TiO2 and helpful to the diffusion of Ti to Si substrate.