Effect of body bias and temperature on low-frequency noise in 40-nm nMOSFETs

This study investigated the effects of temperature and body bias on drain current flicker noise (1/f) in 40-nm nMOSFETs. The 1/f noise is attributable to the charge number fluctuation correlating with the mobility fluctuation. At 300 K, as the depletion width was decreased, 1/f noise decreased with the body bias from − 0.5 to + 0.5 V in the weak inversion; conversely, 1/f noise was independent of the body bias because of the neglected depletion charge capacitance in the strong inversion. When the temperature was below 150 K, 1/f noise increased when the drain voltage was low because of the Fermi level toward the band edge, which has a higher trap density and corresponds to the inverse square of the subthreshold swing. However, when the drain voltage was high, 1/f noise was dominated by the mobility fluctuation because a wider strong inversion region at 150 K resulted in a lower 1/f noise and insignificant body effect. The analysis of this behavior in 40-nm devices may assist in determining the optimal device fabrication methods and circuit design.     

Research on optimizing the noise figure of low noise amplifier method via bias and frequency

In this paper,we present the design of an integrated low noise amplifier(LNA)for wireless local area network(WLAN)applications in the 5.15-5.825 GHz range using a SiGe BiCMOS technology.A novel method that can determine both the optimum bias point and the frequency point for achieving the minimum noise figure is put forward.The method can be used to determine the optimum impedance over a relevant wider operating frequency range.The results show that this kind of optimizing method is more suitable for the WLAN circuits design.The LNA gain is optimized and the noise figure(NF)is reduced.This method can also achieve the noise match and power match simultaneously.This proposal is applied on designing a LNA for IEEE 802.11a WLAN.The LNA exhibits a power gain large than 16 dB from 5.15 to 5.825 GHz range.The noise figure is lower than 2 dB.The OIP3 is 8 dBm.Also the LNA is matched to 50 Ω input impedance with 6 mA DC current for differential design.     

Effect of FN stress and gate-oxide breakdown on high-frequency noise characteristics in deep-submicrometer nMOSFETs

The impact of Fowler-Nordheim (FN) stress and oxide breakdown on high-frequency noise characteristics in 0.18 /spl mu/m nMOSFET has studied. Noise characteristics of the devices at different leakage levels and breakdown hardness are compared. The results have shown a strong dependence of degradation of noise parameter on the gate leakage. The degradation mechanisms are analyzed by extraction of the channel and gate noise using a noise equivalent circuit model. It has been found that gate shot noise, which is commonly ignored in the as-processed nMOSFET, plays a dominant role in determining the high frequency noise in the post-oxide breakdown nMOSFET. The effect of FN stress and oxide breakdown is negligible.     

Effects of carrier heating on laser dynamics-a Monte Carlo study

The static and dynamic properties of semiconductor quantum-well (QW) lasers have traditionally been analyzed by using rate equations that couple cold carriers to photons in the lasing cavity. This assumption of cold carriers, however, has often been disputed because it does not account for heating due to carrier relaxation, hot phonon effects, and spectral hole burning. All these processes affect laser performance significantly by modifying the gain because gain depends on carrier temperature as well as spectral broadening. In this paper, we study the carrier dynamics of QW lasers using a Monte Carlo method and conclude that hot carrier effects in semiconductor lasers are important and need to be considered for the analysis and design of semiconductor lasers     

New experimental findings on hot carrier effects in deep submicrometer surface channel PMOS

The correlation between gate current and substrate current in surface channel(SC) PMOS with effective channel length down to 0.15 μm is investigated within the general framework of the lucky-electron model. It is found that the impact ionization rate increases, but the device degradation is not serious in deep submicrometer PMOS. To extend the lucky-electron model to deep submicrometer regime, we empirically model the effective pinch-off length as a function of the gate length and the gate bias voltage. SCIHE is suggested as the possible physical mechanism for the enhanced impact ionization and the gate current reduction.     

An experimental study on transport issues and electrostatics of ultrathin body SOI pMOSFETs

We present an experimental study of the transport properties (low field hole mobility /spl mu//sub h/) and electrostatics (threshold voltage V/sub th/, and gate-to-channel capacitance C/sub gc/) of ultrathin body (UTB) SOI pMOSFETs using a large RingFet structure. Body thicknesses were /spl sim/4.3 nm to 50 nm. We find that 1) hole mobility decreases significantly as T/sub Si/<10 nm, and tends to show negligible dependence on the transverse electric field for extremely thin T/sub Si/ (<6 nm) and 2) a V/sub th/ shift of /spl sim/150 mV occurs over the studied T/sub Si/ range, accompanied by enhancement of weak inversion capacitance in thin body devices. Simulations were performed to provide insight into the experimental observations.     

The role of carbon on performance of strained-Si:C surface channel NMOSFETs

Carbon incorporation in strained-Si surface channel NMOSFET is investigated. Due to the ～52% lattice mismatch between silicon and carbon, the channel is expected to have higher strain than strained-Si, indicating that the carrier mobility can be enhanced significantly. There is a ～40% electron mobility enhancement for incorporated carbon content of 0.25% in strained-Si NMOSFETs compared to unstrained Si channels. The performance of channels with increased strain is not as high as theoretical predictions. This is due to the large D_it at the oxide/strained-Si:C interface and alloy scattering, which degrades carrier mobility enhancement.     

An ultra-low-power CMOS voltage reference generator based on body bias technique

A CMOS voltage reference, based on body bias technique, has been proposed and simulated using SMIC 0.18 μm CMOS technology in this paper. The proposed circuit can achieve a temperature coefficient of 19.4 ppm/°C in a temperature range from −20 °C to 80 °C, and a line sensitivity of 0.024 mV/V in a supply voltage range from 0.85 V to 2.5 V, without the use of resistors and any other special devices such as thick gate oxides MOSFETs with higher threshold voltage. The supply current at the maximum supply voltage and at 27 °C is 214 nA. The power supply rejection ratio without any filtering capacitor at 10 Hz and 10 kHz are −88.2 dB and −36 dB, respectively.     

Temperature dependence of channel mobility in HfO/sub 2/-gated NMOSFETs

The degradation mechanisms of effective electron channel mobility in HfO/sub 2/-gated nMOSFETs have been studied by analyzing experimental data at various temperatures from 120 to 320 K. The major finding is that, while significant Coulomb scattering plays an important role in causing the observed mobility degradation, it does not account for all of the degradation; rather, it requires an extra phonon scattering mechanism, beyond that arising from the phonons in the Si substrate, to explain our experimental results. This extra phonon scattering mechanism has been found to exhibit relatively weak temperature dependence, and is attributed to the soft optical phonons in the HfO/sub 2/ layer.     

An analysis of small-signal substrate resistance effect in deep-submicrometer RF MOSFETs

Two different explanations of the S/sub 22/ kink phenomenon in deep-submicrometer RF MOSFETs have been reported: Hjelmgren and Litwin (see IEEE Trans. Electron Devices, vol.48, no.2, p.397-399, 2001) attributed the phenomenon to the substrate resistance, while Lu et al. (see ibid., vol.49, no.2, p.333-340, 2001) concluded that it results from the transconductance, or simply speaking, the size of the transistor. In this paper, we extend the dual-feedback circuit methodology for the three-terminal FET model proposed by Lu et al. into a more general four-terminal model in order to account for the influence of the substrate resistance. Our results show that, for a given MOSFET, either substrate resistance or transconductance may cause a kink in S/sub 22/. In addition to the single kink, which results from the above two factors, the double kinks, which appear when the substrate resistance of a MOSFET is within a middle range (approximately 10/sup 2/ to 10/sup 4/ /spl Omega/), can also be accounted for by our extended model. Experimental data representative of 0.25 /spl mu/m gate MOSFETs are adopted to verify our theory. Excellent agreement between theoretical values and experimental data has been found, which indicates our theory can successfully explain the S/sub 22/ kink phenomenon in deep-submicrometer RF MOSFETs.     

Comments on hot carrier noise in field-effect transistors

Taking into account more rigorously such high field effects as velocity saturation and an increasing free carrier temperature, a new derivation is presented for the output noise of the field-effect transistor. It is shown that for devices with a short channel and a high saturation voltage the equivalent noise resistance can increase considerably above the low field value.     

Effect of contact-etch-stop-layer and Si1-xGex channel mechanical properties on nano-scaled short channel NMOSFETs with dummy gate arrays

The layout effect influences the performance of nanoscale devices with advanced strain engineering, considering that the size of a technology node continuously shrinks to ≤ 20 nm. Transistors with a long gate width could be fabricated, and the portion that protrudes outside the channel region could be located on a soft shallow trench isolation region and even across the dummy active region of diffusion. Induced strained silicon technology should be considered when managing and enhancing mobility gain in devices with narrow channel widths. Thus, we fabricated a 20 nm silicon-based n-type metal-oxide-semiconductor field-effect transistor with a Si_0.75Ge_0.25 alloy channel and a + 3.0 GPa tensile contact etch stop layer as stressors. The transistor was utilized at different dummy gate arrays and dummy poly pitches. The fabricated device was subjected to oriented stress simulation, and the relationship between the piezoresistance effect and the stress component within the device channel was investigated. The best performance, which was 40% higher than that of conventional transistors, was observed in the transistor with 100 nm gate width.     

Effects of hot phonons on carrier heating in quantum-well lasers

The hot phonon effects on carrier heating in quantum-well lasers are theoretically investigated. We show that the neglect of the finite lifetime of LO phonons will significantly underestimate the carrier energy relaxation time and thus underestimate the effect of carrier heating in quantum-wed lasers. We investigate the effects of carrier heating with hot phonons on the saturation and degradation of the resonant frequency in high-speed quantum-well lasers. The implications of the hot phonon effects on the design of high-speed quantum-well lasers are also discussed     

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.     

An experimental study on the quality-of-service of video encoded sequences over an emulated rain-faded Satellite channel

Video-coding techniques that are widely used in videoconferencing and streaming applications over the Internet may face degradation in performance when traversing satellite channels. The aim of the present paper is to provide objective measurements of the quality of video-encoded sequences for two of the most popular video coders in this setting [namely, H.261 and moving picture experts group (MPEG)-2], after transmission over faded satellite channels. In particular, the emphasis is on the Ka band, which is becoming an attractive alternative for commercial applications but is more prone to quality degradation than the currently widely used Ku band. In order to test the behavior of the coders in repeatable experimental conditions and over different data link platforms, two transmission chains have been implemented in the laboratory by careful emulation of the required environment. The data link layer has been based on HDLC-like and direct video broadcasting protocols, respectively. The experiments have been performed in the presence of additive white Gaussian noise (AWGN) and by using fading patterns derived by real-world data. The results obtained highlight some often neglected aspects in the behavior of the coders under examination, both in relation to their comparative performance and to their adaptability to different underlying data link protocols.     

An experimental study on the intensity of scattering wave byautomobile body as multipath source in mobile communications

The measurement of the electromagnetic wave scattering pattern of a reduced automobile model by means of a microwave simulation experiment in an electromagnetic anechoic chamber is discussed. The results show that the maximum level of the automobile's scattering pattern reaches -10 to -22 dB compared with the incident wave intensity. This indicates that when a mobile station is in a heavy-traffic city zone, the scattering from vehicles in the vicinity of the station must be taken into account as a source of multipath     

磁光盘载噪比测试方法的研究

通过深入研究载噪比测试过程,找出了测试中存在的特殊性,根据这种特殊性,提出了一种简单有效的数据采集方法,即单轴等时间采样法.     

Effect of carrier lifetime on mode partition noise in multimodesemiconductor lasers

The dependence of mode partition noise (MPN), and its association with the eye diagram and power penalty, on carrier lifetime in 1.3 μm InGaAsP multimode semiconductor lasers for a 1.2 Gbit/s lightwave transmission system was investigated. It was found that lasers with shorter carrier lifetimes showed less MPN, and hence, a better eye opening and a lower power penalty, than the lasers with longer carrier lifetimes. The significant dependence of MPN, eye opening, and power penalty on carrier lifetime in multimode semiconductor lasers suggests that the carrier lifetime of the laser, which depends on the laser design, can be used as an important parameter for characterizing the performance of high-speed lightwave transmission systems     

RCS信道快速载波同步设计

RCS信道具有用户多、时钟同步要求高和帧长较短等特点,因而要求快速的同步搜索。为了实现RCS信道快速载波同步,在帧结构中专门设计了惟一字,将基于惟一字的载波同步算法和基于Viterbi-Viterbi算法的二次相位估计相结合,设计了易于实现的载波同步方案。经Matlab仿真,证明了方案的性能。所用设计可简单快速实现相位同步,并在某卫星终端应用中取得了明显的效果。     

Characteristics of upstream channel noise in CATV-networks

Currently there is a growing demand towards interactive multimedia services using high capacity hybrid fibre-coax (HFC) CATV-networks. With regards to the realisation of upstream traffic, many problems occur with the accumulation of noise due to the tree and branch architecture of the coaxial access network. The properties of the spectral noise signature resulting from the accumulation of noise have been studied by performing measurements in two major CATV-networks in Europe. Serious noise accumulation was found with levels up to resp. -70 dBm and -50 dBm in the two networks. Interference from short-wave broadcasting caused interference levels up to resp. -60 dBm and -40 dBm. We show that upstream noise is time dependent, and is not only caused by CATV-network subscribers