GaAs MESFET低频噪声机理的研究

<正> GaAs MESFET器件的低频噪声是该器件一项重要的电特性,研究它的产生机理对器件微波非线性和从直流到微波超宽带等方面的应用,以及了解器件内部深能级均非常重要。 GaAs MESFET低频噪声研究在国内尚未见到有关文献报道。在建立了GaAs MESFET低频噪声测量系统的基础上,作者对南京电子器件研究所研制生产的各种GaAs MESFET样管及HEMT器件进行了测量。这些器件的低频噪声具有以下特点:(1)器件低频噪声同器件的偏置状态和几何参数有关,其等效输入噪声电压随源—漏电流和栅偏电压绝对值的增加而增大,但随栅长和栅宽的增加而减小。并发现功率器件噪声较低。(2)GaAs MESFET低频噪声比Si器件大。(3)一般器件的低频噪声谱呈1/f~μ关系,其中α=11;而GaAs MESFET的α在0.5～2之间。(4)HEMT器件的低频噪声同GaAs器件相比稍大。     

GaAs MESFET器件低频噪声机理研究

本文报道了对各种GaAs MESFET和HEMT器件的低频噪声测量和讨论,认为这些器件低频噪声具有以下特点:(1)GaAs MESFET器件低频噪声随器件源、漏电流、负栅压绝对值增大而增大。(2)GaAs MESFET低频噪声一般比硅器件噪声大2～3个数量级。(3)GaAs MESFET低频噪声不是纯1/f噪声,其噪声谱与频率成1/f~a关系,d值在0.5～2之间。 作者首次将高能电子辐照技术用于研究GaAs MESFET器件的低频噪声。通过对辐照前后器件变温噪声测量,并结合DLTS技术和变频C—V等方法,对器件低频噪声产生机理进行了实验探讨。认为GaAs MESFET的低频噪声主要是器件体内深能级陷阱的产生—复合噪声。器件表面特性、结特性对器件低频噪声有影响,但不是主要来源。 作者认为,对短沟道GaAs MESFET器件而言,速度饱和效应对共低频噪声有影响。因而从基本二维泊松方程出发,计入速度饱和区产生—复合噪声对器件低频噪声的贡献,首次得到了正常工作(高源、漏电压)条件下,器件低频噪声的理论计算模型,理论和实验吻合较好。     

GaAs MESFET器件低频噪声机理的实验研究

本文介绍了GaAs MESFET器件低频噪声测量系统,以及该器件低频噪声的特点。在分析器件中低频噪声可能来源的基础上,首次采用高能电子辐照技术并结合变温噪声测量、变频C-V等方法,对器件低频噪声产生机理进行了实验研究。     

GaAs微波功率FET的可靠性与功率特性的关系

采用射频最大饱和漏电流和射频击穿电压解释了影响GaAs微波功率FET功率特性的主要因素,GaAs FET栅漏间半导体表面负电荷的积累在引起器件电流偏移的同时还导致器件微波功率特性的退化,GaAs微波功率FET的可靠性和功率特性相互关联,高可靠的GaAs微波功率FET一定具有高性能的功率特性。在器件工艺中对表面态密度和陷阱能级密度严格控制是实现GaAs微波功率FET的高功率特性和高可靠性的关键。     

GaAs PHEMT开关模型的研究

论述了GaAs PHEMT开关器件的建模,介绍了利用微波电路设计软件ADS建立GaAs PHEMT开关模型的方法,给出了模型模拟与器件测量的曲线和模型参数.提取开关模型是研制控制电路的关键,特别是对于MMIC电路.一种0.5μm GaAs PHEMT开关器件模型已开发成功,并集成在ADS环境中,可为各类开关、衰减器和移相器等微波控制电路提供可靠的器件模型,提高电路设计精度.     

SiGe HBT低频噪声PSPICE模拟分析

对SiGe HBT低频噪声的各噪声源进行了较全面的分析,据此建立了SPICE噪声等效电路模型,进一步用PSPICE软件对SiGe HBT的低频噪声特性进行了仿真模拟.研究了频率、基极电阻、工作电流和温度等因素对低频噪声的影响.模拟结果表明,相较于Si BJT和GaAs HBT,SiGe HBT具有更好的低频噪声特性;在低频范围内,可通过减小基极电阻、减小工作电流密度或减小发射极面积、降低器件的工作温度等措施来有效改善SiGe HBT的低频噪声特性.所得结果对SiGe HBT的设计和应用有重要意义.     

适于宽带放大器应用的GaAs MESFET设计和微波性能

本文讨论适于宽带应用的微波低噪声GaAs MESFET的设计理论,并在4GHz下,计算了器件最小噪声系数、最小噪声源电阻、最小噪声源电抗和等效噪声电阻,讨论了器件的微波性能,并应用计算机辅助设计计算出器件的S参数。     

用于GaAs功率MESFET的新型钝化膜

用直流反应溅射淀积的AlN薄膜对GaAs功率MESFET进行了钝化。给出了钝化后器件的直流特性。器件的直流参数BVGD、IDSS和Vp在钝化后几乎没有改变。还给出了器件的微波特性。实验证明，AlN钝化的器件性能较好，它是一种很有前途的GaAs钝化材料。     

SiGe HBT噪声的研究进展

噪声对RF电路设计非常关键,故需要对SiGe HBT噪声特性进行深入研究。根据器件的高频噪声模型,指出了影响SiGe HBT高频噪声参数的主要因素,论述了优化设计的具体方法;举例说明尺寸缩小使得高频噪声性能已经达到了GaAs pHEMT的水平,fT达到了375 GHz。分析了SiGe HBT低频噪声的机理和模型及其与几何尺寸的关系,指出用fC/fT表达低频噪声性能更合适;举例说明小尺寸效应使得SiGe HBT的低频噪声偏离了1/f噪声形式。     

薄膜电阻器件的低频噪声测试方法研究

薄膜电阻器件的低频有色噪声是器件内部微观结构影响的缩影，承载了大量的与器件结构和工艺水平相关的信息，往往能够反映器件的内在质量和可靠性的优劣。本文给出了薄膜电阻器件低频噪声测试的一般方法并探讨了样品在低阻和裸片情况下进行低频噪声信号测试应采用的技巧和注意事项，还讨论了探针接触噪声对测试结果的影响，对正确的噪声信号采集和器件可靠性评估有重要意义。     

Reliability of Power Gaas FET's-Au Gates and Al-Au Linked Gates

An investigation of the reliability of two types of commercial microwave power GaAs FET's has been carried out. Mean-time-to-failure data for a device mounted face-up with Al gates but without an Al-Au couple is presented and similar data for a "flip-chip" mounted Au-refractory gate device is reviewed. The failure mechanisms for both devices are described.     

Reliability of III–V based heterojunction bipolar transistors

This paper reviews the reliability of III-V based heterojunction bipolar transistors (HBTs). These devices have many potential advantages over other solid-state microwave devices. However, because of the tradeoff between performance and reliability, they are not being used to any great extent in power microwave applications. In the type of III-V HBT device most fully developed, the AlGaAs/GaAs HBT, leakage currents play a major role in the dominant mode of degradation. Because low-frequency noise is related to these leakage currents it has been used extensively in the analysis of the performance and reliability limitations of these devices. The reliability of other types of III-V HBT devices, such as InGaP/GaAs and InP based devices, is also discussed.     

A theory of noise in GaAs FET microwave oscillators and its experimental verification

A theory has been developed which provides an entirely analytical approach to the calculation of AM and FM noise in free-running GaAs FET microwave oscillators. The theory is based on the model that low-frequency device noise is mixed with the carrier signal via the nonlinearity of the FET and upconverted to microwave frequencies. Because of the analytical nature of the theory, all the important device and circuit parameters on which the noise generation depends are explicitly given. Two GaAs FET oscillators have been fabricated and used to investigate the FM noise. The theory predicts well both the spectral dependence and the absolute magnitude of the FM noise in both oscillators. The noise performance of the oscillators differs by 19 dB. The theory indicates that no single factor is responsible for this, and moreover that attention should be given to the optimization of many device and circuit features in the design of a low noise FET oscillator.     

Relation between low-frequency noise and long-term reliability ofsingle AlGaAs/GaAs power HBTs

Self-aligned AlGaAs/GaAs single heterojunction bipolar transistors (HBTs) were fabricated using an advanced processing technology for microwave and millimeter-wave power applications. These devices were processed simultaneously, on different epilayers with similar layer structure design supplied from different vendors. They showed similar dc characteristics (current gain, β=30) and their microwave performance was also identical (f_T=60 GHz, f_max=100 GHz). The HBTs showed different noise and reliability characteristics depending on their epilayer origin. HBT's from the high-reliability wafer showed MTTF of 10⁹ h at junction temperature of 120°C. They also presented very small 1/f noise with corner frequencies in the range of a few hundred Hz. Devices were subjected to bias and temperature stress for testing their noise and reliability characteristics. Stressed and unstressed devices showed generation-recombination noise with activation energies between 120-210 meV. Stress was found to increase the generation-recombination noise intensity but not its activation energy. These HBTs did not show any surface-related noise indicating that processing did not significantly influence noise characteristics. It was found that the base noise spectral density at low frequency can be correlated to the device long term reliability     

150 GHz GaAs MITATT source

The performance of a GaAs Schottky barrier transmit-time source is described. The device is reversed biased into mixed tunnel-avalanche breakdown. A CW output power of 3 mW with 1/2% conversion efficiency has been measured at 150 GHz. This is the highest frequency CW GaAs source built to date and has many potential applications in systems requiring a low noise local oscillator in near millimeter microwave integrated circuits.     

GaAs-based materials for heterojunction bipolar transistor's: reliability results and MMIC applications

This paper reports the present status of GaAs based-heterojunction bipolar transistor (HBT) under development at Thales. We have developed a complete GaInP/GaAs-based technological process from material studies to discrete devices and microwave monolithic integrated circuits (MMIC) realisations. This know-how has been transferred recently to Thales/United monolithic semi-conductors. Discrete devices with output power over 1 W and power added efficiency (PAE) over 50% have been obtained at 10 GHz in CW. 8 W MMIC amplifiers have been fabricated using the same unit cells. The first reliability results are promising: more than 6000 h without failure for devices stressed up to 210°C and 40 kA cm⁻². However, it seems that these results can still be improved. Some physical properties of the GaInP/GaAs HBT structures are suspected to have a major impact on the device reliability. The role of key parameters such as hydrogen incorporation in the GaAs base layer or residual strain in the GaInP/GaAs HBT structure has been investigated and its effects on the device characteristics identified. However, the major reliability improvement came from a novel way to passivate the extrinsic base surface. A comparison of the obtained results (device performance and reliability) with some of the best reported values in the literature (HP, TI, Daimler-Benz, etc.) is presented.     

Design and Performance of X-Band Oscillators with GaAs Schottky-Gate Field-Effect Transistors

The circuit construction and design of an X-band oscillator with a GaAs Schottky-gate FET have been studied. The oscillation characteristics including stability and noise performance have been examined in order to clarify the position of a GaAs FET as a microwave solid-state oscillator device. The experiments have revealed that 1) the GaAs FET simultaneously possesses the most desirable features of both Gunn and IMPATT oscillators, i.e., low bias voltage operation and fairly high efficiency, and 2) it is situated between Gunn and GaAs IMPATT oscillators with respect to noise properties. The results indicate that the GaAs FET oscillator will soon be joining the family of microwave solid-state oscillators as a promising new member.     

Thermal modeling of power gallium arsenide microwave integratedcircuits

Manufacturers are developing power devices for ever higher frequencies using GaAs MESFETs and heterojunction bipolar devices constructed with III-V compounds on GaAs substrates, as well as integrated power devices on monolithic microwave integrated circuits (MMICs). A problem with the technology is the low thermal conductivity of gallium arsenide, giving rise to thermal design problems that must be solved if good reliability is to be achieved. A three-dimensional numerical simulator is used to study this problem. In particular, the approximations which are possible in performing realistic assessments of the thermal resistance of typical GaAs power device structures under steady-state conditions are examined     

HBT电压控制振荡器的相位噪声

研究了电压控制振荡器（ＶＣＯ）的相位噪声与构成该振荡器的有源器件的低频噪声的关系,测试了ＳｉＢＪＴ、ＡｌＧａＡｓ／ＧａＡｓ ＨＢＴ和ＧａＩｎＰ／ＧａＡｓ ＨＢＴ的低频噪声,并分析了各自低频噪声产生的原因,提出了选择ＧａＩｎＰ／ＧａＡｓ ＨＢＴ ＶＣＯ来实现微波固体振荡器低相位噪声化这一发展方向。     

Power gain and noise of InP and GaAs insulated gate microwave FETs

LPE GaAs and InP n-channel depletion mode insulated gate field effect transistors (MISFETs) having 4 μm gate lengths have been fabricated employing pyrolytic Si_xO_yN_z, pyrolytic SiO₂ and an anodic dielectric for gate insulation.The microwave power gain, noise figure, maximum output power and power-added efficiency were measured and compared to those parameters measured on GaAs Schottky barrier gate devices of identical geometry. The results show that, at least at the microwave frequencies measured, power gain and noise are essentially the same in the GaAs Schottky gate FET and anodic MISFET devices while the maximum output power of a typical InP MISFET was greater than that of a representative GaAs Schottky device.