Common Base Four-Finger InGaAs/InP Double Heterojunction Bipolar Transistor with Maximum Oscillation Frequency 535 GHz

A common base four-finger InOaAs/InP double heterojunction bipolar transistor with 535 OHz fmax by using the 0.5 μm emitter technology is fabricated. Multi-finger design is used to increase the input current. Common base configuration is compared with common emitter configuration, and shows a smaller K factor at high frequency span, indicating a larger breakpoint frequency of maximum stable gain/maximum available gain （MSG/MAG） and thus a higher gain near the cut-off frequency, which is useful in THz amplifier design.

Physical modeling of direct current and radio frequency characteristics for In P-based InAlAs/InGaAs HEMTs

Direct current（DC） and radio frequency（RF） performances of InP-based high electron mobility transistors（HEMTs）are investigated by Sentaurus TCAD. The physical models including hydrodynamic transport model, Shockley–Read–Hall recombination, Auger recombination, radiative recombination, density gradient model and high field-dependent mobility are used to characterize the devices. The simulated results and measured results about DC and RF performances are compared, showing that they are well matched. However, the slight differences in channel current and pinch-off voltage may be accounted for by the surface defects resulting from oxidized InAlAs material in the gate-recess region. Moreover,the simulated frequency characteristics can be extrapolated beyond the test equipment limitation of 40 GHz, which gives a more accurate maximum oscillation frequency( f;) of 385 GHz.

Improvement on Frequency Performance of SOI SiGe HBT

Based on the advantages of SOI technology, the frequency performance of SiGe HBT with SOI structure has been simulated. Compared with bulk SiGe HBT, the results show that the buried oxide layer （BOX） can reduce collector-base capacitance CCB with the maximum value 89.3%, substrate-base capacitance CSB with 94. 6%, and the maximum oscillation frequency is improved by 2.7. The SOl structure improves the frequency performance of SiGe HBT, which is adaptable to high-speed and high power applications.

Radio-frequency transistors from millimeter-scale graphene domains

Graphene is a new promising candidate for application in radio-frequency （RF） electronics due to its excellent elec- tronic properties such as ultrahigh carrier mobility, large threshold current density, and high saturation velocity. Recently, much progress has been made in the graphene-based RF field-effect transistors （RF-FETs）. Here we present for the first time the high-performance top-gated RF transistors using millimeter-scale single graphene domain on a SiO2/Si substrate through a conventional microfabrication process. A maximum cut-off frequency of 178 GHz and a peak maximum os- cillation frequency of 35 GHz are achieved in the graphene-domain-based FET with a gate length of 50 nm and 150 nm, respectively. This work shows that the millimeter-scale single graphene domain has great potential applications in RF devices and circuits.

Carrier frequency offset estimation for a generalized OFDMA uplink

A residual carrier frequency offset （CFO） estimation scheme is proposed for the uplink of orthogonal frequency division multiple access （OFDMA） systems. Multiple access interference caused by CFOs in the uplink is investigated, as it severely affects the performance of a classical maximum likelihood （ML） frequency estimator. By the use of the estimated CFOs of the active users, the linear maximum mean square error （LMMSE） equalization is performed before the ML frequency estimator for the interference cancellation, which can help to sufficiently improve the estimation accuracy for the residual CFO of the incoming user. Analysis and simulations show that the modified ML estimator provides a tradeoff between estimation accuracy and computational complexity caused by the LMMSE interference cancellation, and the proposed method allows OFDMA systems flexibly allocating subcarriers to users.

In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As HEMTs with f_(max) of 183GHz

By epitaxial layer structure design and key fabrication process optimization,a lattice-matched InP-based In0.53Ga0.47 As-In0.52Al0.48As HEMT with an ultra high maximum oscillation frequency （fmax） of 183GHz was fab- ricated. The fmax is the highest value for HEMTs in China. Also, the devices are reported, including the device structure, the fabrication process, and the DC and RF performances.

Mechanism of Pendulum-type wave phenomenon in deep block rock mass

Pendulum-type ( μ wave) wave is a new type of elastic wave propagated with low frequency and low velocity in deep block rock masses. The μ wave is sharply different from the traditional longitudinal and transverse waves propagated in continuum media and is also a phenomenon of the sign-variable reaction of deep block rock masses to dynamic actions, besides the Anomalous Low Friction (ALF) phenomenon. In order to confirm the existence of the μ wave and study the rule of variation of this μ wave experimentally and theoretically, we first carried out one-dimensional low-speed impact experiments on granite and cement mortar blocks and continuum block models with different characteristic dimensions, based on the multipurpose testing system developed by us independently. The effects of model material and dimensions of models on the propagation properties of 1D stress wave in blocks medium are discussed. Based on a comparison and analysis of the propagation properties (acceleration amplitudes and Fourier spectra) of stress wave in these models, we conclude that the fractures in rock mass have considerable effect on the attenuation of the stress wave and retardarce of high frequency waves. We compared our model test data with the data of in-situ measurements from deep mines in Russia and their conclusions. The low-frequency waves occurring in blocks models were validated as Pendulum-type wave. The frequencies corresponding to local maxima of spectral density curves of three-directional acceleration satisfied several canonical sequences with the multiple of 2～(1/2), most of those frequencies satisfied the quantitative expression (2～(1/2))i V p/2△ .

Emotion Detection by Analyzing Voice Signal Using Wavelet

Emotion is such a unique power of human trial that plays a vital role in distinguishing human civilization from others. Voice is one of the most important media of expressing emotion. We can identify many types of emotions by talking or listening to voices. This is what we know as a voice signal. Just as the way people talk is different, so is the way they express emotions. By looking or hearing a person’s way of speaking, we can easily guess his/her personality and instantaneous emotions. People’s emotion and feelings are expressed in different ways. It is through the expression of emotions and feelings that people fully express his thoughts. Happiness, sadness, and anger are the main medium of expression way of different human emotions. To express these emotions, people use body postures, facial expressions and vocalizations. Though people use a variety of means to express emotions and feelings, the easiest and most complete way to express emotion and feelings is voice signal. The subject of our study is whether we can identify the right human emotion by examining the human voice signal. By analyzing the voice signal through wavelet, we have tried to show whether the mean frequency, maximum frequency and Lp values conform to a pattern according to its different sensory types. Moreover, the technique applied here is to develop a concept using MATLAB programming, which will compare the mean frequency, maximum frequency and Lp norm to find relation and detect emotion by analyzing different voices.

Device research on GaAs-based InAlAs/InGaAs metamorphic high electron mobility transistors grown by metal organic chemical vapour deposition

This paper applies a novel quad-layer resist and e-beam lithography technique to fabricate a GaAs-based InAlAs/InGaAs metamorphic high electron mobility transistor （HEMT） grown by metal organic chemical vapour deposition （MOCVD）. The gate length of the metamorphic HEMT was 150 nm, the maximum current density was 330 mA/mm, the maximum transconductanee was 470 mS/mm, the threshold voltage was -0.6 V, and the maximum current gain cut-off frequency and maximum oscillation frequency were 102 GHz and 450 GHz, respectively. This is the first report on tri-termination devices whose frequency value is above 400 GHz in China. The excellent frequency performances promise the possibility of metamorphic HEMTs grown by MOCVD for millimetre-wave applications, and more outstanding device performances would be obtained after optimizing the material structure, the elaborate T-gate and other device processes further.

Impact of symmetric gate-recess length on the DC and RF characteristics of InP HEMTs

We fabricated a set of symmetric gate-recess devices with gate length of 70 nm.We kept the source-to-drain spacing(L_(SD))unchanged,and obtained a group of devices with gate-recess length(L_(recess))from 0.4µm to 0.8µm through process improvement.In order to suppress the influence of the kink effect,we have done SiN_(X) passivation treatment.The maximum saturation current density(ID_(max))and maximum transconductance(g_(m,max))increase as L_(recess) decreases to 0.4µm.At this time,the device shows ID_(max)=749.6 mA/mm at V_(GS)=0.2 V,V_(DS)=1.5 V,and g_(m,max)=1111 mS/mm at V_(GS)=−0.35 V,V_(DS)=1.5 V.Meanwhile,as L_(recess) increases,it causes parasitic capacitance C_(gd) and g_(d) to decrease,making f_(max) drastically increases.When L_(recess)=0.8µm,the device shows f_(T)=188 GHz and f_(max)=1112 GHz.

Radio frequency transistors based on ultra-high purity semiconducting carbon nanotubes with superior extrinsic maximum oscillation frequency

In this paper, we report polyfluorene-separated ultra-high purity semiconducting carbon nanotube radio frequency transistors with a self-aligned T-shape gate structure. Because of the ultra-high semiconducting tube purity and self-aligned T-shape gate structure, these transistors showed an excellent direct current and radio frequency performance. In regard to the direct current characteristics, these transistors showed a transconductance up to 40μS/μm and an excellent current saturation behavior with an output resistance greater than 200 kΩ·μm. In terms of the radio frequency characteristics, an extrinsic maximum oscillation frequency （fmax） of 19 GHz was achieved, which is a record among all kinds of carbon nanotube transistors, and an extrinsic current gain cut-off frequency （fT） of 22 GHz was achieved, which is the highest among transistors based on carbon nanotube networks. Our results take the radio frequency performance of carbon nanotube transistors to a new level and can further accelerate the application of carbon nanotubes for future radio frequency electronics.

Enhancement of fMAX of InP-based HEMTs by double-recessed offset gate process

A double-recessed offset gate process technology for In P-based high electron mobility transistors(HEMTs)has been developed in this paper.Single-recessed and double-recessed HEMTs with different gate offsets have been fabricated and characterized.Compared with single-recessed devices,the maximum drain-source current(I_(D,max))and maximum extrinsic transconductance(g_(m,max))of double-recessed devices decreased due to the increase in series resistances.However,in terms of RF performance,double-recessed HEMTs achieved higher maximum oscillation frequency(f_(MAX))by reducing drain output conductance(g_(m,max))and drain to gate capacitance(C_gd).In addition,further improvement of fMAXwas observed by adjusting the gate offset of double-recessed devices.This can be explained by suppressing the ratio of C_(gd)to source to gate capacitance(C_gd)by extending drain-side recess length(Lrd).Compared with the single-recessed HEMTs,the f;of double-recessed offset gate HEMTs was increased by about 20%.

Impact of gate offset in gate recess on DC and RF performance of InAlAs/InGaAs InP-based HEMTs

A set of 100-nm gate-length In P-based high electron mobility transistors(HEMTs)were designed and fabricated with different gate offsets in gate recess.A novel technology was proposed for independent definition of gate recess and T-shaped gate by electron beam lithography.DC and RF measurement was conducted.With the gate offset varying from drain side to source side,the maximum drain current(I_(ds,max))and transconductance(g_(m,max))increased.In the meantime,fTdecreased while f;increased,and the highest fmax of 1096 GHz was obtained.It can be explained by the increase of gate-source capacitance and the decrease of gate-drain capacitance and source resistance.Output conductance was also suppressed by gate offset toward source side.This provides simple and flexible device parameter selection for HEMTs of different usages.

0.15-μm T-gate In_(0.52)Al_(0.48)As/In_(0.53)Ga_(0.47)As InP-based HEMT with fmax of 390 GHz

In this paper, 0.15-μm gate-length In0.52Al0.48As/In0.53Ga0.47As InP-based high electron mobility transistors （HEMTs） each with a gate-width of 2×50 μm are designed and fabricated. Their excellent DC and RF characterizations are demonstrated. Their full channel currents and extrinsic maximum transconductance （gm,max） values are measured to be 681 mA/mm and 952 mS/mm, respectively. The off-state gate-to-drain breakdown voltage （BVGD） defined at a gate current of-1 mA/mm is 2.85 V. Additionally, a current-gain cut-off frequency （fT） of 164 GHz and a maximum oscillation frequency （fmax） of 390 GHz are successfully obtained; moreover, the fmax of our device is one of the highest values in the reported 0.15-μm gate-length lattice-matched InP-based HEMTs operating in a millimeter wave frequency range. The high gm,max, BVGD, fmax, and channel current collectively make this device a good candidate for high frequency power applications.

Geometry and size optimization of stiffener layout for three-dimensional box structures with maximization of natural frequencies

Based on the growth mechanism of natural biological branching systems and inspiration from the morphology of plant root tips,a bionic design method called Improved Adaptive Growth Method(IAGM)has been proposed in the authors’previous research and successfully applied to the reinforcement optimization of three-dimensional box structures with respect to natural frequencies.However,as a kind of ground structure methods,the final layout patterns of stiffeners obtained by using the IAGM are highly subjected to their ground structures,which restricts the optimization effect and freedom to further improve the dynamic performance of structures.To solve this problem,a novel post-processing geometry and size optimization approach is proposed in this article.This method takes the former layout optimization result as start,and iteratively finds the optimal layout angles,locations,and lengths of stiffeners with a few design variables by optimizing the positions of some specific node lines called active node lines.At the same time,thick-nesses of stiffeners are also optimized to further improve natural frequencies of three-dimensional box structures.Using this method,stiffeners can be successfully separated from their ground structures and further effectively improve natural frequencies of three-dimensional box structures with less material consumption.Typical numerical examples are illustrated to validate the effectiveness and advantages of the suggested method.

70-nm-gated InAlN/GaN HEMTs grown on SiC substrate with f_T/f_(max)>160GHz

lnA1N/GaN high-electron-mobility transistors （HEMTs） on SiC substrate were fabricated and character- ized. Several techniques, consisting of high electron density, 70 nm T-shaped gate, low ohmic contacts and a short drain-source distance, are integrated to gain high device performance. The fabricated InA1N/GaN HEMTs exhibit a maximum drain saturation current density of 1.65 A/ram at Vgs = 1 V and a maximum peak transconductance of 382 mS/rnm. In addition, a unity current gain cut-off frequency （fT） of 162 GHz and a maximum oscillation frequency （fmax） of 176 GHz are achieved on the devices with the 70 nm gate length.

22 nm In0.75Ga0.25As channel-based HEMTs on InP/GaAs substrates for future THz applications

In this work,the performance of Lg = 22 nm In（0.75）Ga（0.25）As channel-based high electron mobility transistor（HEMT） on InP substrate is compared with metamorphic high electron mobility transistor（MHEMT） on GaAs substrate.The devices features heavily doped In（0.6）Ga（0.4）As source/drain（S/D） regions,Si double δ-doping planar sheets on either side of the In（0.75）Ga（0.25） As channel layer to enhance the transconductance,and buried Pt metal gate technology for reducing short channel effects.The TCAD simulation results show that the InP HEMT performance is superior to GaAs MHEMT in terms of fT,f（max） and transconductance（g（mmax））.The 22 nm InP HEMT shows an fT of 733 GHz and an f（max） of 1340 GHz where as in GaAs MHEMT it is 644 GHz and 924 GHz,respectively.InGaAs channel-based HEMTs on InP/GaAs substrates are suitable for future sub-millimeter and millimeter wave applications.

Ultra high-speed InP/InGaAs SHBTs with f_t and f_(max) of 185 GHz

An InP/InGaAs single heterojunction bipolar transistor（SHBT） with high maximum oscillation frequency （fmax） and high cutoff frequency（ft） is reported.Efforts have been made to maximize f（max） and ft simultaneously including optimizing the epitaxial structure,base-collector mesa over-etching and base surface preparation.The measured ft and fmax both reached 185 GHz with an emitter size of 1×20μm^2,which is the highest f_（max） for SHBTs in China's Mainland.The device is suitable for ultra-high speed digital circuits and low power analog applications.

Analysis of DC and analog/RF performance on Cyl-GAA-TFET using distinct device geometry

In this paper, analysis of DC and analog/RF performance on cylindrical gate-all-around tunnel fieldeffect transistor（TFET） has been made using distinct device geometry. Firstly, performance parameters of GAATFET are analyzed in terms of drain current, gate capacitances, transconductance, source-drain conductance at different radii and channel length. Furthermore, we also produce the geometrical analysis towards the optimized investigation of radio frequency parameters like cut-off frequency, maximum oscillation frequency and gain bandwidth product using a 3D technology computer-aided design ATLAS. Due to band-to-band tunneling based current mechanism unlike MOSFET, gate-bias dependence values as primary parameters of TFET differ. We also analyze that the maximum current occurs when radii of Si is around 8 nm due to high gate controllability over channel with reduced fringing effects and also there is no change in the current of TFET on varying its length from 100 to 40 nm.However current starts to increase when channel length is further reduced for 40 to 30 nm. Both of these trades-offs affect the RF performance of the device.

Investigation and statistical modeling of InAs-based double gate tunnel FETs for RF performance enhancement

In this paper,RF performance analysis of In As-based double gate（DG）tunnel field effect transistors（TFETs）is investigated in both qualitative and quantitative fashion.This investigation is carried out by varying the geometrical and doping parameters of TFETs to extract various RF parameters,unity gain cut-off frequency（f_t）,maximum oscillation frequency（f_（max））,intrinsic gain and admittance（Y）parameters.An asymmetric gate oxide is introduced in the gate-drain overlap and compared with that of DG TFETs.Higher ON-current（ION）of about 0.2 mA and less leakage current（IOFF）of 29 f A is achieved for DG TFET with gate-drain overlap.Due to increase in transconductance（g_m）,higher ft and intrinsic gain is attained for DG TFET with gate-drain overlap.Higher f_（max） of 985 GHz is obtained for drain doping of 5×10^（17）cm^（-3） because of the reduced gate-drain capacitance（C_（gd））with DG TFET with gate-drain overlap.In terms of Y-parameters,gate oxide thickness variation offers better performance due to the reduced values of Cgd.A second order numerical polynomial model is generated for all the RF responses as a function of geometrical and doping parameters.The simulation results are compared with this numerical model where the predicted values match with the simulated values.