A unified model for single/multifinger HBTs including self-heatingeffects

This paper presents a unified analytical large-signal model that includes self-heating effects. The model is applied to a single-finger AlGaAs/GaAs heterojunction bipolar transistor (HBT) and a multifinger InGaAs/GaAs HBT. The self-heating effect in the HBT is simulated as a feedback from the collector current to the base-emitter voltage. The main advantage of the circuit presented here is that additional analysis of coupling between electrical and thermal circuits is not required, as is the case with the existing models. The small-signal HBT model is implemented based on the S-parameters at multiple frequencies measured at multiple bias points. This model is verified by comparing the measured and simulated S-parameters. The large-signal model is based on the forward Gummel plot and is built over the small-signal model. This model is verified by comparing the simulated and measured dc I-V characteristics     

Method to determine intrinsic and extrinsic base-collectorcapacitance of HBTs directly from bias-dependent S-parameter data

This letter presents a novel small-signal model extraction procedure which determines intrinsic and extrinsic base-collector capacitance (C_bci and C_bex, respectively) directly from S-parameter data. The procedure utilizes physical assumptions shout the bias dependence of small-signal parameters. The model is validated on several InGaP/GaAs HBTs with different layouts, and the extraction results are discussed. The small-signal model is physical, produces excellent S-parameter fits, and may be used to derive a compact large-signal model     

A large-signal SOI MOSFET model including dynamic self-heatingbased on small-signal model parameters

A new technique for a large-signal SOI MOSFET model with self-heating is proposed, based on thermal and electrical parameters extracted by fitting a small-signal model to measured s-parameters. A thermal derivative approach is developed to calculate the thermal resistance when the isothermal dc drain conductance is extracted from small-signal fitting. The thermal resistance is used to convert the measured dc current-voltage (I-V) characteristics containing the self-heating effects to the isothermal I-V characteristics needed for the large-signal model. Large-signal pulse and sinusoidal input signals are used to verify the model by measurement, and shown to reproduce the observed large-signal behavior of the devices with great accuracy, especially when two or more thermal time constants are used     

An HBT noise model valid up to transit frequency

A comprehensive HBT noise model for circuit simulation is presented that describes the microwave noise behavior up to the transit frequency. It is based on diode noise theory, and requires only the small-signal equivalent circuit, including the thermal resistance, and the dc bias point. A main feature is correlation of the shot-noise sources at the pn junctions. The model is verified by measurements of the four noise parameters of an InGaP/GaAs HBT, varying frequency and bias conditions     

5~6GHz自适应线性化偏置的InGaP/GaAs HBT功率放大器

针对高质量无线局域网的传输需求,设计了一款工作在5~6 GHz的宽带磷化镓铟/砷化镓异质结双极型晶体管(InGaP/GaAs HBT)功率放大器芯片。针对HBT晶体管自热效应产生的非线性和电流不稳定现象,采用自适应线性化偏置技术,有效地解决了上述问题。针对射频系统的功耗问题,设计了改进的射频功率检测电路,以实现射频系统的自动增益控制,降低功耗。通过InGaP/GaAs HBT单片微波集成电路(MMIC)技术实现该功率放大器芯片。仿真结果表明,功放芯片的小信号增益达到32 dB;1 dB压缩点功率为28.5 dBm@5.5 GHz,功率附加效率PAE超过32%@5.5 GHz;输出功率为20 dBm时,IMD3低于-32 dBc。     

A novel temperature-dependent large-signal model of heterojunction bipolar transistor with a unified approach for self-heating and ambient temperature effects

A large-signal modeling of power heterojunction bipolar transistor (HBT) is demonstrated for an accurate simulation of self-heating and ambient temperature effects and nonlinear behaviors such as output power, gain expansion, intermodulation distortion (IMD), and adjacent channel power ratio (ACPR). The physical relationship between the device current and the rate of change in the built-in potential with respect to the device temperature has been utilized for a fully electrothermal modeling. To enable an immediate use for a circuit design, the model extraction was done for in-situ output-stage device from two-stage power amplifier (PA) circuit. In each parameter extraction step, measurement data obtained under a consistent environment, which are current-voltage (I-V) at various temperatures and small-signal S-parameters under various bias conditions, have been carefully examined and utilized to relate the meaning of each parameter to the physical principle of the device. Measurements and simulations are compared for the verification of the model under dc condition at various temperatures.     

一种新的HBT小信号模型参数优化提取法

阐述了一种新的异质结双极型晶体管（HBT）的小信号模型参数提取方法――综合多偏置点优化参数提取法. 对HBT小信号模型进行推导并确定外部参数和内部参数的计算公式;介绍了多偏置点优化算法,并在GaInP/ GaAs HBT器件上进行了鲁棒性和精确性测试. 实验采用了一系列随机初始值,结果表明提取的参数值具有唯一收敛性和精确性,仿真结果与测量数据的相对误差小于1%.     

An Improved Model for GaAs MESFETs Suitable for a Wide Bias Range

In this letter, we present a new large signal model for GaAs metal-semiconductor field effect transistors, incorporating features for enhancing the bias range for which accuracy is maintained, for use in the simulation of microwave circuits. The model parameters for a specific case were extracted from a wide range of dc I-V and S-parameter data, and the simulated behavior was observed to match the measured data closely. The model includes the possibility of showing negative slopes of the I-V curves at high power without sacrificing accuracy in predicting radio frequency behavior, while remaining simple enough for use in simulation tools     

High C-doped base InGaP/GaAs HBTs with improved characteristics grown by MOCVD

The improvement in the emitter-base leakage current of HBTs has been investigated by the use of an InGaP emitter. InGaP/GaAs n-p-n HBT structures with high C-doped bases, grown by MOCVD, have been fabricated and these devices show Gummel plots with near ideal I-V characteristics (n/sub c/=1.00 and n/sub b/=1.09). Measured current gain remains relatively flat over five decades of collector current and its magnitude is greater than unity at collector current as low as 0.1 mu A. The characteristics of these HBTs were compared with fabricated AlGaAs/GaAs HBTs having similar device structure. The superior performance of the InGaP emitter HBT is demonstrated.<>     

具有AlGaAs缓变结构的InGaP/GaAs HBT性能改进分析

对改进型结构具有零导带势垒尖峰的缓变InGaP/AlGaAs/GaAs HBT器件的直流和高频特性进行了理论探讨,并同传统突变结构的InGaP/GaAs HBT的相应性能作了比较。结果表明:在低于30 nm的一定范围内的缓变层厚度下,与突变的InGaP/GaAs HBT相比,改进型结构的InGaP/AlGaAs/GaAs HBT具有更低的offset和开启电压、更强的电流驱动能力、更好的伏-安输出特性和高频特性。     

DC to high-frequency HBT-model parameter evaluation using impedanceblock conditioned optimization

A new heterojunction bipolar transistor (HBT) small-signal equivalent-circuit parameter-extraction procedure employing multibias S-parameter data is presented. The algorithm combines analytical and empirical parameter evaluation techniques and results in a bias-dependent HBT model. To minimize the risk of nonphysical parameter estimation, elements such as the DC transport factor, α_o, and the emitter-base conductance are evaluated from the device DC characteristics, and the frequency dispersion of α is related to the RC time-constant of the emitter-base junction. Moreover, initial values for the extrinsic device parasitics are obtained from “hot” as well as “cold” S-parameter data. The method results in excellent fit between measured and modeled S-parameter data in the frequency range DC-40 GHz and for a wide range of bias operating points     

Electro-thermal stress effect on InGaP/GaAs heterojunction bipolar low-noise amplifier performance

This paper investigates the electro-thermal stress-induced performance degradation of a cascode low-noise amplifier built using advanced InGaP/GaAs heterojunction bipolar transistors. Changes in device characteristics due to the electro-thermal stress are examined experimentally. SPICE Gummel-Poon model parameters extracted from the pre- and post-stress HBT measurement data are then used in Cadence SpectreRF simulator to study the impact of the electro-thermal stress on the InGaP/GaAs LNA’s RF performance.     

Direct extraction and numerical simulation of the base andcollector delay times in double heterojunction bipolar transistors

A new method is presented to evaluate the base and collector transit times, τ_B and τ_C in heterojunction bipolar transistors (BBT's) from the phase and magnitude of the common-base current gain, α(ω), which itself was directly extracted from measured S-parameter data. The method is applied to InGaP/GaAs single and double HBT's. A smaller cutoff frequency in the latter device is attributed to τ_B and τ_C due to two effects: trapping of electrons in the conduction band triangular barrier existing at the base-collector (B-C) heterojunction and smaller saturation velocity of electrons in InGaP as compared to GaAs. Finally, a new B-C design of InGaP/GaAs DNBT's is proposed to partially compensate the transit time effects. Numerical simulation of the cutoff frequency demonstrates the superiority of the proposed structure for high-frequency applications     

Thermal analysis of AlGaN-GaN power HFETs

In this paper, we present a thermal analysis of AlGaN-GaN power heterojunction field-effect transistors (HFETs). We report the dc, small-signal, large-signal, and noise performances of AlGaN-GaN HFETs at high temperatures. The temperature coefficients measured for GaN HFETs are lower than that of GaAs pseudomorphic high electron-mobility transistors, confirming the potential of GaN for high-temperature applications. In addition, the impact of thermal effects on the device dc, small-signal, and large-signal characteristics is quantified using a set of pulsed and continuous wave measurement setups. Finally, a thermal model of a GaN field-effect transistor is implemented to determine design rules to optimize the heat flow and overcome self-heating. Arguments from a device, circuit, and packaging perspective are presented.     

Stepping toward standard methods of small-signal parameterextraction for HBTs

An improved HBT small-signal parameter extraction procedure is presented in which all the equivalent circuit elements are extracted analytically without reference to numerical optimization. Approximations required for simplified formulae used in the extraction routine are revised, and it is shown that the present method has a wide range of applicability, which makes it appropriate for GaAs and InP-based single and double HBTs. Additionally, a new method is developed to extract the total delay time of HBTs at low frequencies, without the need to measure h₂₁ at very high frequencies and/or extrapolate it with -20 dB/dec roll-off. The existing methods of finding the forward transit time are also modified to improve the accuracy of this parameter and its components. The present technique of parameter extraction and delay time analysis is applied to an InGaP/GaAs DHBT and it is shown that: (1) variations of all the extracted parameters are physically justifiable; (2) the agreement between the measured and simulated S- and Z-parameters in the entire range of frequency is excellent; and (3) an optimization step following the analytical extraction procedure is not necessary. Therefore, we believe that the present technique can be used as a standard extraction routine applicable to various types of HBTs     

High-Frequency Noise Modeling of InGaP/GaAs HBT With Base-Contact Capacitance and AC Current Crowding Effect

A heterojunction-bipolar-transistor (HBT) noise model including the base-impedance effect is presented, which takes into account the base-contact capacitance and ac current crowding effect. The proposed noise model describes well the high-frequency noise characteristics of InGaP/GaAs HBTs in the presence of base-impedance effect. Good agreement is observed between the measured and calculated noise parameters for the different sizes of InGaP/GaAs HBTs. We found that the effect of ac current crowding on noise parameters is more critical than that of base-contact capacitance.      

Isothermal DC and microwave characterizations of power RF siliconLDMOSFETs

Presented in this paper are two new approaches for the acquisition of both isothermal DC current-voltage (I-V) characteristics and microwave S-parameters of power RF LDMOSFETs. In the first approach, a 3D tensor product B-spline representation is used to extract isothermal DC I-V characteristics from DC I-V characteristics measured at various substrate temperatures. The average device surface temperature is measured using an infrared sensor. A single effective thermal resistance is found to map the entire electrothermal profile of the device, justifying the isothermal DC I-V definition used. In the second approach, isothermal I-V and microwave data are directly measured with an efficient procedure that keeps the average device surface temperature constant. Excellent agreement is obtained between the numerical extraction and the direct measurement approach. Finally, the comparison of the transconductance extracted from the isothermal DC I-V and microwave data confirms the presence of a small low-frequency dispersion in LDMOSFETs not due to self-heating     

High reliability InGaP/GaAs HBT

Excellent long term reliability InGaP/GaAs heterojunction bipolar transistors (HBT) grown by metalorganic chemical vapor deposition (MOCVD) are demonstrated. There were no device failures (T=10000 h) in a sample lot of ten devices (L=6.4 μm ×20 μm) under moderate current densities and high-temperature testing (J_c=25 kA/cm ², V_ce=2.0 V, Junction Temp =264°C). The dc current gain for large area devices (L=75 μm ×75 μm) at 1 kA/cm² at a base sheet resistance of 240 ohms/sq (4×10 ¹⁹ cm^-3@700 Å) was over 100. The dc current gain before reliability testing (L=6.4 μm ×10 μm) at 0.8 kA/cm² was 62. The dc current gain (0.8 kA/cm²) decreased to 57 after 10000 h of reliability testing. The devices showed an f_T=61 GHz and f_max=103 GHz. The reliability results are the highest ever achieved for InGaP/GaAs HBT and these results indicate the great potential of InGaP/GaAs HBT for numerous low- and high-frequency microwave circuit applications. The reliability improvements are probably due to the initial low base current at low current densities which result from the low surface recombination of InGaP and the high valence band discontinuity between InGaP and GaAs     

High-speed, low-noise InGaP/GaAs heterojunction bipolar transistors

We have demonstrated self-aligned InGaP/GaAs heterojunction bipolar transistors (HBT's) with excellent dc, microwave, and noise performance. A 3×10 μm² emitter finger device achieved a cutoff frequency of f_T=66 GHz and a maximum frequency of oscillation of f_max=109 GHz. A minimum noise figure of 1.12 dB and an associated gain of 11 dB were measured at 4 GHz. These results are the highest combined f_T+f_max and the lowest noise figure reported for an InGaP/GaAs HBT and are attributed to material quality and the use of self-aligned base contacts. These data clearly demonstrate the viability of InGaP/GaAs HBT's for high-speed, low-noise circuit applications