微波功率SiGe HBT的温度特性

通过研究SiGe异质结双极型晶体管(HBT)的温度特性,发现SiGe HBT的发射结正向电压随温度的变化率小于同质结Si双极型晶体管(BJT).在提高器件或电路热稳定性时,SiGe HBT可以使用比Si BJT更小的镇流电阻.同时SiGe HBT共发射级输出特性曲线在高电压大电流下具有负阻特性,而负阻效应的存在可以有效地抑制器件的热不稳定性效应,从而在温度特性方面证明了SiGe HBT更适合于微波功率器件.     

微波功率SiGe HBT的温度特性

通过研究SiGe异质结双极型晶体管(HBT)的温度特性,发现SiGe HBT的发射结正向电压随温度的变化率小于同质结Si双极型晶体管(BJT).在提高器件或电路热稳定性时,SiGe HBT可以使用比Si BJT更小的镇流电阻.同时SiGe HBT共发射级输出特性曲线在高电压大电流下具有负阻特性,而负阻效应的存在可以有效地抑制器件的热不稳定性效应,从而在温度特性方面证明了SiGe HBT更适合于微波功率器件.     

Si/SiGe/Si双异质结晶体管(HBT)的负阻特性

同质结硅双极晶体管在共射极状态下工作中,在高集电极--发射极电压、大电流下,由于热电正反馈,容易发生热击穿,这限制了晶体管的安全工作区域.本文报道了在大电流下,由于热电负反馈,重掺杂基区Si/SiGe/HBT出现了负阻特性,并对这一现象进行了新的解释,认为这是由于大电流下耗散功率增加,基区俄歇复合导致电流增益随温度增加而减小的结果.这一现象有利于改善大电流下双极晶体管的抗烧毁能力,证明Si/SiGe/HBT适于大功率应用.     

Ge_xSi_(1-x)/Si异质结器件的研制现状

介绍了应变层Ge_xSi_(1-x)/Si异质结构的生长、材料特性及其在异质结双极晶体管(HBT)、双极反型沟道场效应晶体管(BICFET)、调制掺杂场效应晶体管(MODFET)、谐振隧道二极管、负阻效应晶体管(NERFET)、毫米波混合隧道雪崩渡越时间(MITATT)二极管和光电探测器等器件中的应用状况,并指出了其发展前景。     

GexSi1—x／Si异质结器件的研制现状

介绍了应变层GexSi1-x/Si异质结构的生长，材料特性及其在异质结双极晶体管（HBT），双极反型沟道场效应晶体管（BICFET），调制掺杂场效应晶体管（MODFET），谐振隧道二极管，负阻效应晶体管（NERFET），毫米波混合隧道雪崩渡越时间（MITATT）二极管入和光电探测器等器件中的应用状况，并指出了其发展前景。     

Si／SiGe／Si双异质结晶体管（HBT）物负阻特性

同质结硅双极晶体管在共射极状态下工作中,在高集电极－发射极电压、大电流下,由于热电正反馈,容易发生热击穿,这限制了晶体管的安全工作区域。本文报道了在大电流下,由于热电负反馈,重掺杂基区Si/SiGe/HBT出现了负阻特性,并对这一现象进行了新的解释,认为这是由于大电流下耗散功率增加,基区俄歇复合导致电流增益随温度增加而减小的结果。这一现象有利于改善大电流下双极晶体管的抗烧毁能力,证明Si/SiGe/HBT适于大功率应用。     

锗硅异质结双极晶体管空间辐射效应研究进展

异质结带隙渐变使锗硅异质结双极晶体管(SiGe HBT)具有良好的温度特性,可承受-180~+200 ℃的极端温度,在空间极端环境领域具有诱人的应用前景。然而,SiGe HBT器件由于材料和工艺结构的新特征,其空间辐射效应表现出不同于体硅器件的复杂特征。本文详述了SiGe HBT的空间辐射效应研究现状,重点介绍了国产工艺SiGe HBT的单粒子效应、总剂量效应、低剂量率辐射损伤增强效应以及辐射协同效应的研究进展。研究表明,SiGe HBT作为双极晶体管的重要类型,普遍具有较好的抗总剂量和位移损伤效应的能力,但单粒子效应是制约其空间应用的瓶颈问题。由于工艺的不同,国产SiGe HBT还表现出显著的低剂量率辐射损伤增强效应响应和辐射协同效应。     

一种新型SGOI SiGe异质结双极型晶体管

为了改善SiGe异质结双极型晶体管(HBT)的电学特性和频率特性,设计了一种新型的SGOI SiGe HBT。在发射区引入了双轴张应变Si层。多晶Si与应变Si双层组合的发射区有利于提高器件的注入效率。利用Silvaco TCAD软件建立了二维器件结构模型,模拟了器件的工艺流程,并对器件的电学特性和频率特性进行了仿真分析。结果表明,与传统的SiGe HBT相比,新型SGOI SiGe HBT的电流增益β、特征频率fT等参数得到明显改善,在基区Ge组分均匀分布的情况下,β提高了29倍,fT提高了39.9%。     

SiGe异质结双极晶体管的基区优化

对应用于高频微波功率放大器的SiGe异质结双极晶体管(HBT)的基区进行了优化.研究发现,器件对基区Ge组分以及掺杂浓度十分敏感.采用重掺杂基区,适当提高Ge组分并形成合适的浓度分布,可以有效地改进SiGe HBT的直流特性,同时能够提高器件的特征频率.晶体管主要性能的提高使SiGe HBT技术在微波射频等高频电子领域得到更加广泛的应用.     

低相位噪声HBT单片压控振荡器的设计

与传统的硅双极晶体管(Si BJT)相比,异质结双极晶体管(HBT)具有特征频率高、1/f噪声小的优点,可以用在微波频段内的单片集成电路设计中。采用异质结双极晶体管(HBT)设计一种低相位噪声HBT单片VCO电路,芯片电路测试结果:电压控制频率范围fo=8.0~9.5 GHz;输出功率Pout=7~9.5 dBm;在偏离振荡中心频率foffset为100 kHz时相位噪声Pn=-106 dBc/Hz。     

SiGe HBT与Si BJT的~(60)Co射线总剂量辐照效应比较

研究了国产结构参数近似的SiGe HBT与Si BJT在60Coγ射线辐照前和不同剂量辐照后性能的变化,并作了比较。辐照后集电极电流Ic变化很小,基极电流Ib明显增大,表明辐照后电流增益的下降主要是由于Ib的退化所导致。当辐照剂量达到10kGy(Si)时,SiGe HBT和Si BJT的最大电流增益分别下降为77%和55%,表明了SiGe HBT具有比Si BJT更好的抗γ射线辐照性能。对辐射损伤机理进行了探讨。     

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.     

Performance comparison of state-of-the-art heterojunction bipolar devices (HBT) based on AlGaAs/GaAs, Si/SiGe and InGaAs/InP

This paper presents a comprehensive comparison of three state-of-the-art heterojunction bipolar transistors (HBTs); the AlGaAs/GaAs HBT, the Si/SiGe HBT and the InGaAs/InP HBT. Our aim in this paper is to find the potentials and limitations of these devices and analyze them under common Figure of Merit (FOM) definitions as well as to make a meaningful comparison which is necessary for a technology choice especially in RF-circuit and system level applications such as power amplifier, low noise amplifier circuits and transceiver/receiver systems. Simulation of an HBT device with an HBT model instead of traditional BJT models is also presented for the AlGaAs/GaAs HBT. To the best of our knowledge, this work covers the most extensive FOM analysis for these devices such as I-V behavior, stability, power gain analysis, characteristic frequencies and minimum noise figure. DC and bias point simulations of the devices are performed using Agilent's ADS design tool and a comparison is given for a wide range of FOM specifications. Based on our literature survey and simulation results, we have concluded that GaAs based HBTs are suitable for high-power applications due to their high-breakdown voltages, SiGe based HBTs are promising for low noise applications due to their low noise figures and InP will be the choice if very high-data rates is of primary importance since InP based HBT transistors have superior material properties leading to Terahertz frequency operation.     

Applications and processing of SiGe and SiGe:C for high-speed HBT devices

The continued growth of high-speed-digital data transmission and wireless communications technology has motivated increased integration levels for ICs serving these markets. Further, the increasing use of portable wireless communications tools requiring long battery lifetimes necessitates low power consumption by the semiconductor devices within these tools. The SiGe and SiGe:C materials systems provide solutions to both of these market needs in that they are fully monolithically integratible with Si BiCMOS technology. Also, the use of SiGe or SiGe:C HBTs for the high-frequency bipolar elements in the BiCMOS circuits results in greatly decreased power consumption when compared to Si BJT devices.Either a DFT (graded Ge content across the base) or a true HBT (constant Ge content across the base) bipolar transistor can be fabricated using SiGe or SiGe:C. Historically, the graded profile has been favored in the industry since the average Ge content in the pseudomorphic base is less than that of a true HBT and, therefore, the DFT is tolerant of higher thermal budget processing after deposition of the base. The inclusion of small amounts of C (e.g. <0.5%) in SiGe is effective in suppressing the diffusion of B such that very narrow extremely heavily doped base regions can be built. Thus the f_T and f_max of a SiGe:C HBT/DFT are capable of being much higher than that of a SiGe HBT/DFT.The growth of the base region can be accomplished by either nonselective mixed deposition or by selective epitaxy. The nonselective process has the advantage of reduced complexity, higher deposition rate and, therefore, higher productivity than the selective epitaxy process. The selective epi process, however, requires fewer changes to an existing fabrication sequence in order to accommodate SiGe or SiGe:C HBT/DFT devices into the BiCMOS circuit.     

Mechanically strained Si-SiGe HBTs

The current gain (/spl beta/=I/sub C//I/sub B/) variations of the mechanically strained Si-SiGe heterojunction bipolar transistor (HBT) and Si bipolar junction transistor (BJT) devices are investigated experimentally and theoretically. The /spl beta/ change of HBT is found to be 4.2% and -7.8 under the biaxial compressive and tensile mechanical strain of 0.028%, respectively. For comparison, there are 4.9% and -5.0 /spl beta/ variations for BJT under the biaxial compressive and tensile mechanical strain of 0.028%, respectively. In HBT, the mechanical stress is competing with the compressive strain of SiGe base, inherited from the lattice misfit between SiGe and Si. The current change due to externally mechanical stress is the combinational effects of the dependence of the mobility and the intrinsic carrier concentration on strain.     

SiGe HBT的速度优化设计

从理论分析角度介绍了优化SiGe异质结晶体管速度的方法。结合双极晶体管的工艺限制，介绍了SiGeHBT的基本原理，讨论了SiGeHBT的发射区／基区／集电区设计。最后，以一个100GHzfmax和fT的HBT为例，对电路制作工艺参数进行了讨论。     

High injection effects on noise characteristics of Si BJTs and SiGe HBTs

We present a physically based comparison of the current spectral densities in a SiGe heterojunction bipolar transistors (HBT) and a Si bipolar junction transistor (BJT) of identical geometry and doping levels, based on the direct evaluation of emitter, base and collector current fluctuations. An ensemble Monte Carlo (EMC) simulator self-consistently coupled with a 2D Poisson solver has been employed for the calculations. In the studied bias range, the largest reduction of the RF current noise values in the HBT as compared with the BJT derives from the spectral density of base current fluctuations, S_JB, and from the spectra of the cross-correlation between emitter and base current fluctuations, S_JBJE. This is due to the fact that the base current in the HBT is strongly reduced as a consequence of the lower gap of the SiGe base. At low injection, the collector spectral density S_JC exhibits a typical shot noise response while S_JB is governed by thermal noise. At high injection, the presence of hot carriers in the base–collector junction (which are less important in the HBT than in the BJT due to the SiGe/Si hetero-interface), the high carrier concentration in the base and the base push-out provokes the deviation of S_JC from the pure shot behavior. Under these conditions, the S_JB term can be neglected in the total noise analysis of the HBT for lower values of J_C, than in the BJT due to the Ge content benefits.     

Theoretical small-signal performance of Si/SiGe/Si HBT

Application of the Monte Carlo technique to analyze electron and hole transport in bulk Si_0.8Ge_0.2 and strained Si _0.8Ge_0.2/Si is discussed. The computed minority- and majority-carrier transport properties were used in a comprehensive small-signal model to evaluate the high-frequency performance of a state-of-the-art n-p-n heterostructure bipolar transistors (HBT) fabricated with SiGe as the base material. The valence band discontinuity of a SiGe-base HBT reverses the degradation in emitter injection efficiency caused by bandgap narrowing in the base, and permits a higher ratio of base doping to emitter doping than would be practical for a bipolar transistor. Any degradative effect of increased base doping on electron and hole mobilities is offset by improved transport in the strained SiGe base, resulting in a marked decrease in the base resistance and base transit time. Compared to the Si BJT, the use of Si_0.8Ge_0.2 for the base region of an HBT leads to significant improvements in low-frequency common emitter current gain, low-frequency unilateral power gain, and maximum oscillation frequency     

On the operation configuration of SiGe HBTs based on power gain analysis

The power gain difference, under different device stability conditions, between common-emitter (CE) and common-base (CB) bipolar junction transistors (BJT) is analyzed comprehensively. The analysis reveals that the CB configuration offers higher maximum available power gain than the CE configuration in the device's high operation frequency range, while the inverse relation holds in the very low frequency range. In the intermediate frequency range, the base resistance value, mainly affected by the base doping concentration, determines which configuration offers higher maximum stable power gain (MSG). These analyses have explicit implications on the operation configurations of SiGe heterojunction bipolar transistors (HBTs). Employing a typical doping profile of Si bipolar junction transistors with a trapezoidal Ge profile in SiGe HBTs usually results in a larger base resistance than the emitter resistance. For these devices, the CE configuration exhibits higher MSG than the CB configuration. Employing a higher base doping concentration than the emitter with a box-type Ge profile considerably reduces the base resistance and thus favors the CB configuration for power amplification in this frequency range. The analysis are quantitatively verified with simulation and measurement results from SiGe HBTs of representative Ge and base doping profiles.     

SiGe/Si HBT高频噪声特性研究

基于器件Y参数,对Si/Si1-xGexHBT的高频噪声进行了模拟。Si/Si1-xGexHBT的高频最小噪声系数随Ge组份x的增加而减小。与Si BJT相比,Si/SiGe HBT具有优异的高频噪声特性。