0.2～30GHz GaAs FET开关模型的提取与验证

在GaAs单片微波集成电路(MMIC)设计中,准确的器件模型对于提高电路设计成功率和缩短电路研发周期起着重要作用。首先采用标准的GaAs MMIC工艺制造出不同栅指数和单位栅宽的开关PHEMT器件,然后对加工的开关电路在"开"态(Vgs=0 V)和"关"态(Vgs=-5 V)进行宽频率范围内的测量,基于测量结果建立起一个参数化的GaAs PHEMT开关等效电路模型,最后通过单刀单掷(SPST)开关来验证参数化模型。应用该参数化模型设计的电路实测与仿真结果基本吻合,证明参数化的GaAs PHEMT模型是可用的。该模型可用于30 GHz以下GaAs PHEMT工艺开关MMIC电路仿真设计。     

Subthreshold current ion GaAs MESFETs

The authors present experimental data that show that the drain-to-source voltage dependence of the subthreshold current in GaAs MESFETs is determined by the variation of threshold voltage with drain-source voltage and not by Schottky-barrier lowering. This model, incorporating gate-to-drain and gate-to-source diode currents, is shown to be in good agreement with measured data. The model is incorporated into a GaAs circuit simulator and is suitable for GaAs IC design     

Effect of iso-electronic dopants on the dislocation density of GaAs

The addition of 1% In to LEC GaAs has been reported to reduce the dislocation density in this material; similar data exists for Sb doping. Several effects have been inferred to explain these phenomena, the most prevailing one stating that the solid stoichiometry is affected by an as yet unknown mechanism. Similar postulations have been made to explain the growth of semi-insulating GaAs. A thermodynamic model is described, based on earlier work, that shows a broadening of the existence region of GaAs when In or Sb are added to GaAs. Comparing the solidus phase diagrams of In- or Sb-doped GaAs to undoped GaAs shows that addition of either one of these two iso-electronic dopants has a similar effect on the solid stoichiometry as adding more As to the melt. However, the increased pressure problems in LEC growth of GaAs, normally associated with adding As, are circumvented if instead In or Sb are added to the melt. From our calculations it is also shown that the addition of the iso-electronic dopants Al or P to GaAs would not result in the same effect on the solid stoichiometry. Published experimental evidence supports this and shows that no dislocation reduction and semi-insulating GaAs is obtained with the use of these dopants. The model described in this paper explains the postulation that iso-electronic doping is of critical significance in controlling the solid stoichiometry and thereby obtaining zero dislocation density LEC GaAs and semi-insulating GaAs.     

基于GaAs STATZ模型的RF MOSFET DC建模技术

STATZ模型是表征GaAsMESFET特性的常用模型,具有表达式简洁、参数少的优点。通过尝试将STATZ模型用于表征射频MOSFET的直流特性,提取并在ADS软件中优化了STATZ直流模型的参数。为了提高仿真精度,模型必须考虑晶体管漏极与源极的寄生电阻,根据MOSFET处于强反型区且漏-源电压为零时的等效电路模型提取了晶体管的漏极和源极的寄生电阻。在ADS软件中利用STATZ模型对MOSFET的直流特性进行了仿真,测量的MOSFET直流曲线与仿真曲线一致性很好,验证了模型的良好的精确度,证明了GaAs STATZ模型可以用于表征射频MOSFET的直流特性。晶体管采用中芯国际的0.13μm RF CMOS工艺制作。     

Analytical model of GaAs MESFET's

A simple analytical model of GaAs MESFET's is proposed. The model is based on the assumption that the current saturation in GaAs MESFET's is related to the stationary Gunn domain formation at the drain side of the gate rather than to a pinchoff of the conducting channel under the gate. The saturation current, channel conductance, transconductance, charge under the gate, gate-to-source and drain-togate capacitances, cutoff frequency, characteristic switching time, power-delay product, and breakdown voltage are calculated in the frame of this model. The results are verified by two-dimensional computer calculations. They agree well with the results of the computer analysis and experimental data for a 1-µm gate GaAs MESFET. It is shown that a stray gate-to-drain and gate-to-source capacitance sets up a limitation of a gate length which must be larger than or about 0.1 µm for a GaAs MESFET.     

Small-signal modeling and parameter extraction method for a multigate GaAs pHEMT switch

This paper presents an accurate small-signal model for multi-gate GaAs pHEMTs in switching-mode.The extraction method for the proposed model is developed.A 2-gate switch structure is fabricated on a commercial 0.5μm AlGaAs/GaAs pHEMT technology to verify the proposed model.Excellent agreement has been obtained between the measured and simulated results over a wide frequency range.     

X射线三轴晶衍射法测量半绝缘GaAs单晶的化学配比

采用X射线三轴晶衍射法,根据As间隙原子对作为过量As在GaAs单晶材料中存在的主要形式的模型,可以无损、高精度测量半绝缘GaAs单晶的化学配比.并探讨了引起晶格变化的原因及其与熔体组分的关系,对于制备高质量GaAs单晶及其光电器件具有重要的意义.     

Analytic theory for current-voltage characteristics and fielddistribution of GaAs MESFET's

The two-dimensional Poisson equation has been solved analytically to obtain the potential and field distribution in the saturation regime of GaAs MESFETs. A physical analytic model is developed for output current-voltage characteristics and for describing the behavior of electrons in GaAs FETs. In this model, the Chang-Fetterman equation is used to approximate the electron drift velocity versus electric field. The resulting l-V curves are in excellent agreement with experimental data. The field distribution and the electron concentration and velocity profiles are consistent with the physical behavior of electrons in GaAs MESFETs     

Projections of GaAs solar-cell performance limits based ontwo-dimensional numerical simulation

The development of a comprehensive, two-dimensional numerical model for AlGaAs/GaAs solar cells is described. The model was used to identify loss mechanisms in present-day high-efficiency GaAs cells and to make realistic projections of attainable cell efficiencies. Numerical simulations show that achievable efficiencies of conventional heteroface cells made on high-quality GaAs films exceed 30% under 500 suns (AM1.5 direct spectrum). Both p-n and n-p cells are adversely affected by bandgap narrowing in p⁺ GaAs. For n-p cells, the use of heterojunction back-surface fields is advantageous and results in an increase of about 1.5% in efficiency. When the Shockley-Read-Hall lifetime parameters are set to infinity, the efficiency increases by only another 0.7%, which demonstrates that bulk material quality is not the major limiting factor in present-day cells. These efficiency projections, which are based on detailed device simulation and realistic material parameters, are only a few percentage points below the thermodynamic limit for GaAs cells     

Comparison of GaAs MESFET and GaAs p-i-n diodes as switch elements

The Kurokawa-Schlosser quality factor Q̂ is used to compare the GaAs MESFET switch with the GaAs p-i-n diode switch. The MESFET device parameters are governed by the power handling capability and the specified pinchoff voltage, and the switch Q̂ is calculated from an approximate expression. The GaAs p-i-n has been characterized using a simple diode model which is derived from detailed simulations. The comparison for typical devices shows that the GaAs pin has the higher Q̂ and therefore should have improved characteristics as a switch in terms of insertion loss and isolation.     

GaAs MESFET circuit simulation model including negative differential mobility

A simple one-dimensional GaAs MESFET model for circuit simulation is presented which takes into account negative differential mobility. In this model, the drain current is derived from the electric field strength at the source side edge under the gate using a gradual depletion layer approximation. The calculated I/V characteristics agree well with the experimental data for GaAs power MESFETs, which show negative differential resistances. The proposed model can be used in computer aided design of GaAs integrated circuits and amplifiers with the great advantage of a small calculation time compared with that of 2-dimensional analysis.     

Role of deep-level centers in compensated semi-insulating GaAs

Requirements are defined for GaAs materials intended for solid-state detectors of ionizing radiation. A model is proposed to ascertain the role of deep-level centers in compensated semi-insulating GaAs. The model consists of transport equations and a charge-balance equation describing carrier transitions in a multi-level system. Its numerical analysis is performed to ascertain the relationship to be satisfied by dopant concentrations.     

Interface states model for III–V oxide interfaces

A general model of the density of interface states at III–V oxide interfaces is presented. The interface states arise from the native defects, such as Ga or As dangling bonds and Ga–Ga or As–As like-atom bonds created by oxidation. As–As bonds are a likely cause of states at the conduction band edge of GaAs. The model explains the difficulty of n-type operation for GaAs FETs compared to GaAs pFETs or to InGaAs nFETs.     

大信号设计GaAs MESFET功率合成

利用ＧａＡｓＭＥＳＦＥＴ功率特性的线性化模型，求出ＧａＡｓＭＥＳＦＥＴ近似最佳功率负载阻抗，为利用谐波平衡法计算提供初值。然后，使用自行研制的谐波平衡分析软件包，进行ＧａＡｓＭＥＳＦＥＴ大信号模型参数的提取和非线性电路模拟计算。将两只总栅宽为９．６ｍｍ的ＧａＡｓＭＥＳＦＥＴ管芯，利用内匹配功率合成技术，在Ｃ波段（５．５～５．８ＧＨＺ）制成１ｄＢ压缩功率大于８Ｗ，典型功率增益９ｄＢ的ＧａＡｓＭＥＳＦＥＴ内匹配功率管。     

Influence of nonuniform field distribution on frequency limits of GaAs field-effect transistors

A simple model which describes well the nonequilibrium electron transport in GaAs using the fit to the equilibrium Monte Carlo data is suggested. In the frame of this model, the cutoff-frequency/gate-length curves are calculated for uniform and nonuniform channel field distribution in GaAs f.e.t.s. The results show that the nonhomogeneity of the electric field in the channel can considerably decrease (by 30%) the maximal frequency of GaAs f.e.t.s.     

GaNAs/GaAs量子阱的静压光致发光研究

在 1 5 K和 0～ 9GPa静压范围下测量了 Ga N0 .0 1 5As0 .985/ Ga As量子阱的光致发光谱。观察到了 Ga NAs阱和 Ga As垒的发光 ,发现 Ga NAs阱发光峰随压力的变化比 Ga As垒发光峰要小很多。当压力超过 2 .5 GPa后还观察到了与 Ga As中的 N等电子陷阱有关的一组新发光峰。用二能级模型及测得的 Ga As带边和 N等电子能级的压力行为计算了 Ga NAs发光峰随压力的变化 ,但计算结果与实验结果相差甚大 ,表明二能级模型并不完全适用。对观察到的 Ga NAs发光峰的强度和半宽随压力的变化也进行了简短讨论。     

Boundary-condition-induced current overshoot in short GaAs samples

The effect of boundary conditions on current overshoot observed in transient nonstationary simulations of electron transport in submicrometer bars of GaAs is described. Noting that the one-valley model for GaAs does not give rise to observable overshoot when the spatially independent Boltzmann transport equation (BTE) is solved, significant current overshoot is reported when the same model is used in the solution of the spatially dependent BTE with replacement boundary conditions. The spatially unidimensional, time-dependent BTE is solved for undoped GaAs samples with lengths varying between 0.2 and 1 μm. The amount of current overshoot varies depending on the length of the sample and is seen to be as high as 10%. The phenomenon is explained using the moments of the Boltzmann equation     

红外GaAs液晶光阀一维等效电路模型分析

叙述了红外GaAs液晶光阀的工作原理和主要构成,并由此建立了红外GaAs液晶光阀一维等效电路模型,根据此模型着重分析光电导层GaAs的厚度对红外液晶光阀的红外调制动态范围、驱动频率和分辨率的影响,给出了部分相关曲线,得到最佳GaAs厚度范围。根据此模型计算出液晶光阀的结构参数,重新设计了液晶光阀并给出了部分实验结果。     

退火损伤对Er注入GaAs和Yb注入InP发光的影响

本文报道了CaAs∶Er、InP∶Yb发光样品的二次离子质谱、X-射线双晶衍射测量结果及其与Er离子的表面成份的关系.分析讨论了退火损伤对GaAs∶Er和InP∶Yb发光的影响以及Er~(3+)复合体发光中心模型.