Scaling characteristics of fNQS and ft in NMOSFETs with uniform and non-uniform channel doping

Extensive process and device simulations are performed to investigate the non-quasi-static transition frequency (f_NQS ) and unity gain frequency (f_t ) behaviour of the NMOSFETs at different technology nodes, varying from 0.5?µm to 90?nm. The scaled transistors are constrained to have identical leakage current (I_OFF ) at scaled voltages to facilitate a fair comparison. f_NQS exhibits a turn-around in the 100?nm regime irrespective of the channel engineering. We attribute this effect to the reduced gate over-drive (V_GS-V_t ) and lower mobility; which inturn degrades the transconductance (g_m ). f_t also shows a similar trend. The turn around effect of f_NQS and f_t disappears, when I_OFF constraint is relaxed or the gate over-drive is increased.     

改善SiGe HBT击穿电压特征频率优值的集电区优化设计

本文利用BVCES×fT代替BVCEO×fT来表征SiGe的击穿电压特征频率优值,其与SiGe HBT集电区设计更具有相关性且更具有实际意义。相比于传统通过减少集电区掺杂浓度来提高击穿电压特征频率优值,本文通过在集电极空间电荷区引入一组复合的N-和P 层来调节CB结附件的电场,降低碰撞电离率,能够在轻微损失特征频率的前提下,较大程度提高BVCES和BVCEO,进而提高了BVCES×fT和BVCEO×fT,突破了“Johnson Limit”。     

Analog and radio-frequency performance analysis of silicon-nanotube MOSFETs

This work presents a comparative study of the influence of various parameters on the analog and RF properties of silicon-nanotube MOSFETs and nanowire-based gate-all-around (GAA) MOSFETs. The important analog and RF performance parameters of SiNT FETs and GAA MOSFETs, namely drain current (I_d), transconductance to drain current ratio (g_m/I_d), I_on/I_off, the cut-off frequency (f_T) and the maximum frequency of oscillation (f_MAX) are evaluated with the help of Y- and H-parameters which are obtained from a 3-D device simulator, ATLAS^TM. It is found that the silicon-nanotube MOSFETs have far more superior analog and RF characteristics (g_m/I_d, f_T and f_MAX) compared to the nanowire-based gate-all-around GAA MOSFETs. The silicon-nanotube MOSFET shows an improvement of~2.5 and 3 times in the case of f_T and f_MAX values respectively compared with the nanowire-based gate-all-around (GAA) MOSFET.     

Electro-ultrasonic spectroscopy of polymer-based thick film layers

We have studied the properties of polymer-based thick film layers by electro-ultrasonic spectroscopy. Electro-ultrasonic spectroscopy method is based on the interaction between ultrasonic vibrations and electrical conductivity of solids. The ultrasonic vibrations of frequency f_U change the contact area between conducting grains in the thick film structure and then the resistance is modulated by the frequency of ultrasonic excitation. An intermodulation voltage is created on this structure. It depends on the value of AC current varying with frequency f_E and on the ultrasonic excited resistance change ΔR varying with frequency f_U. We have measured the intermodulation voltage U_m for a set of polymer-based thick film resistors made by different resistive pastes. It was found that for given sample the intermodulation component of frequency f_m = f_E − f_U increases linearly with electric excitation for the constant ultrasonic excitation. We have normalized the intermodulation voltage U_m by the electric current I_E and this quantity is proportional to the ultrasonic excited resistance change ΔR. The relative resistance change ΔR/R_X is of the order of 10⁻⁷–10⁻⁴. From the comparison of the results measured for the samples made by the same resistive pastes it follows, that relative resistance change ΔR/R_X can be used as an indicator of sample quality.     

Photonic theory of noise

The paper proposes that 1/f noise in materials and devices under non-equilibrium conditions is of electromagnetic origin rather than being related to charge carriers. For samples represented by simple resistors the analysis shows that the noise is due to the discrete nature of photons constituting the impinging electromagnetic flux from the source feeding the resistor. The paper presents detailed analysis of the external and internal electromagnetic fields of the resistor environment, with appropriate interpretation in terms of discrete photons. From quantum theory photons are known to retain their energy under interactions in linear environments. This property implies a departure from macroscopic electromagnetics in that photons cannot be partially transmitted and partially reflected, a phenomenon requiring appropriate modifications of boundary conditions at the resistor surface. These special demands call for inclusion of a supplementary internal resistor mode, serving as a lossless idler which is active only for matching purposes. At the resistor terminals the impinging photons give rise to excitation of RF current and voltage noise with an exact 1/f frequency distribution, which is in agreement with all available experimental measurements. The paper presents detailed formulae for noise spectral densities under general drive conditions from DC and RF sources of arbitrary internal resistance. The presented theoretical noise formulae have the same form as earlier empirical formulae for 1/f noise. With an RF source at frequency f₀ the analysis predicts noise with 1/|f-f₀| frequency distribution, which is compatible with available experimental observations.     

Improved temperature model of AlGaN/GaN HEMT and device characteristics at variant temperature

In this paper, an improved temperature model for AlGaN/GaN high electron mobility transistor (HEMT) is presented. Research is being conducted for a high-performance building block for high frequency applications that combine lower costs with improved performance and manufacturability. The effects of channel conductance in the saturation region and the parasitic resistance due to the undoped GaN buffer layer have been included. The effect of both spontaneous and piezoelectric polarization induced charges at the AlGaN/GaN heterointerface has been incorporated. The proposed model is used to determine the transfer characteristics, output current-voltage characteristics and small-signal microwave parameters of HEMTs. The investigated temperature range is from 100–600 K. The small signal microwave parameters have been evaluated to determine the unity current gain cut-off frequency (f _T ). High f _T (10–70 GHz) values and high current levels (～550 mA/mm) are achieved for a 1 μm AlGaN/GaN HEMTs. A custom DC measurement system is used to facilitate the DC characterization of the unpackaged GaN HEMT test device. The calculated critical parameters and the simulation results suggest that the performance of the proposed device degrades at elevated temperatures.     

A Flexible Microwave Shield with Tunable Frequency‐Transmission and Electromagnetic Compatibility

Wireless techniques have improved life quality for many. However, the drawbacks like instable signal and high loss in air of electromagnetic interference hinder its further development. One solution is to develop a smart material or device, which can selectively receive a specific frequency (f_s) of electromagnetic wave with less loss, and simultaneously show effective shielding against unwanted waves (frequency is denoted as f_p). A bottleneck has been reached, such that using materials alone is unable to achieve the above due to the limitation of the intrinsic physical properties of materials. Here, a strategy combining the material structure design with a voltage control is proposed to overcome the limitation of materials toward the aforementioned task. The efforts are focused on exploring a suitable electrically tunable material with a sensitive response to an external voltage and the flexibility to be engineered to the needed macrostructure. As a result, the f_s region can be fine‐tuned to 8–8.4, 8–9.3, and 8–10.3 GHz.     

Adaptive orthogonal frequency division multiplexing channel capacity employing diversity in cellular fading environments with symmetric scattering distributions

Gaussian and hyperbolic angle‐of‐arrival probability density functions are used to derive channel capacity of orthogonal frequency division multiplexing transmission employing diversity techniques and adaptive policies in cellular wireless fading environments. The intercarrier interference (ICI) power is quantified and given as a function of Doppler shift f_d, symbol duration T_s, frequency correction ζ and propagation ratio τ. Two scattering distributions, which have been shown to closely fit experimental empirical data, are examined in this paper: (i) Gaussian and (ii) hyperbolic. A new signal‐to‐interference‐and‐noise ratio probability density function is derived as a function of the ICI power using diversity techniques and adaptive policies. From that, effects of f_dT_s, ζ and τ on channel capacity can be discussed. The main contribution of this work is to model ICI as a function of f_d and symbol duration T_s. Two diversity techniques are considered: (i) maximal ratio combining and (ii) selective combining. Three adaptive policies are studied: (i) optimal rate adaptation, (ii) optimal rate and power adaptation and (iii) channel inversion with fixed rate. Closed‐form expressions and bounds on various channel capacity with orthogonal frequency division multiplexing transmission under different scenarios are derived. Copyright © 2012 John Wiley & Sons, Ltd.     

Frequency limitation of metal-oxide varistors

The frequency possibilities of metal-oxide varistors are investigated. An expression is deduced for the limiting frequency f _o of their application. It is also expressed in terms of the catalogue data of commercial varistors or by means of the parameters or the ceramic material. An evaluation of the f _o of ZnO, SnO₂ and SrTiO₃ varistors is made. For ZnO devices f _o has a maximum value (3-5) kHz, but for SrTiO₃ it is 100 Hz. The structure of the varistor's ceramic determines the limiting frequency of their application.     

Frequency bandwidth and conversion loss of a semiconductor heterodyne receiver with phonon cooling of two-dimensional electrons

The temperature and concentration dependences of the frequency bandwidth of terahertz heterodyne AlGaAs/GaAs detectors based on hot electron phenomena with phonon cooling of two-dimensional electrons have been measured by submillimeter spectroscopy with a high time resolution. At a temperature of 4.2 K, the frequency bandwidth at a level of 3 dB (f _{3 dB}) is varied from 150 to 250 MHz with a change in the concentration n _s according to the power law f _3dB ∝ n _s ^−0.5 due to the dominant contribution of piezoelectric phonon scattering. The minimum conversion loss of the semiconductor heterodyne detector is obtained in structures with a high carrier mobility (μ > 3 × 10⁵ cm² V⁻¹ s⁻¹ at 4.2 K).     

Role of nanoscale AlN and InN for the microwave characteristics of AlGaN/(Al,In)N/GaN-based HEMT

A new AlGaN/GaN-based high electron mobility transistor (HEMT) is proposed and its micro-wave characteristics are discussed by introducing a nanoscale AlN or InN layer to study the potential improvement in their high frequency performance. The 2DEG transport mechanism including various sub-band calculations for both (Al,In) N-based HEMTs are also discussed in the paper. Apart from direct current characteristics of the proposed HEMT, various microwave parameters such as transconductance, unit current gain (h ₂₁ = 1) cut-off frequency (f _t ), high power-gain frequency (f _max). Masons available/stable gain and masons unilateral gain are also discussed for both devices to understand its suitable deployment in microwave frequency range.     

Frequency Selectivity via Inner Boundary Conditions for A Self-Powered Multiresonant Acoustic Sensing Array with Broad Bandwidth

This study investigates and proposes innovative approaches to achieve frequency selectivity within a limited space. Traditional multiresonant acoustic devices use individual sensing elements of varying sizes to achieve resonance frequency (f_r), leading to an inability to sense focused acoustic waves, unlike the human ear. A miniaturized, self-powered artificial basilar membrane that incorporates multiresonant features is introduced. Multiple f_r of the diaphragms are developed using inner boundary conditions (iBCs) defined by an adjustable micropatterned elastomeric support (µ-support) and a porous nanofiber (NF) mat. This new approach offers the advantage of all-in-one fabrication, eliminating the need for device area variation or an additional rigid frame typically required in conventional multiresonant acoustic devices. The efficacy of the iBCs in shifting f_r within the vocal frequency ranges is verified via a laser Doppler vibrometer, simulation, and triboelectric output. With its self-powering capabilities based on triboelectric principles, this artificial basilar membrane holds promise for accurately recognizing musical and vocal signals with specific frequency characteristics. With four different iBCs in a total device area of 23 × 23 mm², a tunable four-channel system with f_r ranging from 400 to 3000 Hz is achieved. This advancement enables the sensing of focused acoustic waves, simulating the functionality of an artificial human ear model.     

Frequency-response equalization in integrated current amplifiers with collector—base cross coupling

It is shown that monolithic current amplifiers with collector-base cross coupling can ensure a single-stage amplification up to 40 dB in the frequency range from 0 to 0.1f_c (wheref _c is the cutoff frequency of the transistors). This is possible if the effect of intrinsic positive feedback and a parasitic low-pass filter is suppressed. The equalization procedure is described.     

Experimental study and empirical evaluation of carrier compression and third order intermodulation products of unequal carriers in a communication satellite transponder

Carrier compression and third order intermodulation products of two and three unequal carriers have been studied experimentally using a 36 MHz wide C-band transponder of INSAT-1B satellite. From the experimental data, empirical relations for carrier compression for two unequal carriers have been derived, which agree with the measured data within ±0.5 dB. The empirical relations for carrier compression derived for two unequal carriers have been extended to three unequal carriers and good correlations with measured data have been obtained. Empirical relations for third order intermodulation products of two and three (f₁+f₂-f₃ type) unequal carriers have also been derived.     

Sommerfeld wave (<Emphasis Type="Italic">E</Emphasis><Subscript>00</Subscript> wave) propagating along the cylindrical conductor with a large radius

The technique of solving the dispersion equation for the E ₀₀ wave (Sommerfeld wave), which propagates through a cylindrical conductor with large radius a and finite conductivity σ₁ in the presence of a surrounding lossy dielectric, has been developed. The presented numerical results are obtained by calculating a cylinder with the earth radius and sea water parameters at the frequencies f = 0.0500−0.9554 MHz. It is shown that f ₀ = 0.9554 MHz is the limiting frequency.     

一种宽带的InGaP/GaAs HBT 再生频率分频器

A dynamic divide-by-two regenerative GaP/GaAs heterojunction bipolar transistors （HBTs） frequency divider （RFD） is presented in a 60-GHz-fT Intechnology. To achieve high operation bandwidth, active loads instead of resistor loads are incorporated into the RFD. On-wafer measurement shows that the divider is operating from 10 GHz up to at least 40 GHz, limited by the available input frequency. The maximum operation frequency of the divider is found to be much higher than fT/2 of the transistor, and also the divider has excellent input sensitivity. The divider consumes 300.85 mW from 5 V supply and occupies an area of 0.47 × 0.22 mm^2.     

Low sensitivity multifunction active circuits using CFA-based supercapacitor

Some new current feedback amplifier (CFA)-based active Resistance–Capacitance (RC) circuits are presented for the realization of an ideal grounded supercapacitor (Y(s)?=?s ² D) type Frequency Dependent Negative Resistance (FDNR). The D-element is then resonated with additional RC sections to derive multifilter function circuits. The filter function have been tested for continuous resonant frequency (f ₀) tunability in a range of 30?KHz?≤?f ₀?≤?300?KHz with high quality (1?Q?相似文献   

用于太赫兹InP基PHEMTs 1~110GHz全频段在片测试的系统校准方法的对比研究

本文分别采用Multiline-TRL (Thru-Reflect-Line)和LRM (Line-Reflect-Match) 在片系统校准方法,与传统的SOLT (Short-Open-Load-Thru) 校准方法在InP基PHEMTs片上S参数测试方面进行定量的对比。首次在70 KHz~110 GHz全频段实现一次校准,减小了传统的分段测试多次校准带来的系统误差,校准更加方便简单。对比结果表明,基于Multiline-TRL校准和LRM校准后测量的S参数一致,且均优于传统的SOLT校准方法,尤其是在高频段结果更加准确。首次基于拐点进行外推,且器件展现了优良的射频特性,包括最大电流增益截止频率ft= 247 GHz,最大振荡频率fmax= 392 GHz,其准确度高于传统的基于无拐点进行的外推。首次基于LRM校准测得器件的1~110 GHz全频段S参数,建立了器件的1~110 GHz全频段小信号模型,而非基于传统的通过低频测试数据外推获得。     

半导体超晶格太赫兹倍频器研究

提出一种基于电场驱动的GaAs基微带超晶格高阶谐波产生的太赫兹倍频器,利用平衡方程方法分析了倍频器在磁场下峰值功率输出和在参数空间(E_dc,E_ac)的分布情况。研究表明,在(E_dc,E_ac)的参数平面内,磁场对二次和三次谐波功率的峰值影响不大,但磁场会拓宽谐波输出功率的峰值区域,提高在(E_dc,E_ac)参数空间内输出峰值功率的概率。当E_ac确定时,谐波发射功率峰值的位置会受到直流电场产生的布洛赫振荡频率f_B、交流电场产生的调制布洛赫振荡频率f_MB和磁场引起的回旋振荡频率f_c的影响而发生变化。研究表明,基于半导体超晶格的太赫兹倍频器是很有应用潜力的太赫兹波发生器件。     

<Emphasis Type="Italic">f</Emphasis><Subscript>T</Subscript> × <Emphasis Type="Italic">BV</Emphasis><Subscript>cbo</Subscript> product modeling for SiGe:C HBTs

The specific aspects of SiGe:C HBT process and device simulation using TCAD are discussed. Cut-off frequency f _T and collector junction breakdown voltage BV _cbo dependences on carbon concentration in SiGe base area are investigated. The boron and carbon profiles in SiGe base are obtained to provide a trade-off between gain, cut-off frequency and break-down voltage. High values of f _T × BV _cbo product were achieved.