非晶硅发射区双极晶体管的低温特性

本文研究了非晶硅发射区双极晶体管的低温特性，得出了如下结论：低温下电流增益随基区杂质浓度的上升而下降，不同于常规同质结双极晶体管的情况，集电极电流则随基区杂质浓度的上升而上升。这些结果将为低温双极晶体管的设计提供理论依据。     

硅低温双极晶体管的优化设计与制备─—I．优化设计理论

本文研究了硅双极晶体管电流增益和截止频率的低温物理特性，提出了电流增益在低温下将随发射区杂质浓度的下降和基区杂质浓度的上升而上升的新理论，得出了低温下硅中浅能级杂质将起有效陷阱作用的新结论。在上述基础上，本文对发射区、基区和收集区的掺杂分布进行了优化设计，这将成为获得高性能硅低温双极晶体管的重要设计依据和理论基础。     

硅低温双极晶体管的优化设计与制备：I.优化设计理论

本文研究了硅双极晶体管电流增益和截止频率的低温物理特性，提出了电流增益在低温下将随发射区杂质浓度的下降和基区杂质浓度的上升而上升的新理论，得出了低温下硅中浅能级杂质将起有效陷阱作用的新结论。在上述基础上，本文对发射区、基区和收集区的掺杂分布进行了优化设计，这将成为获得高性能硅低温双极晶体管的重要设计依据和理论基础。     

硅低温双极晶体管的优化设计与制备：II结构与电特性分析

本文在前文器件掺杂分布优化设计的基础上，实现了结构设计和工艺选择，采用多晶硅发射极技术，研制成功了７７Ｋ下高增益（ＨＦＥ可达２５０）硅双极晶体管；采用多晶硅发射区和基区重掺杂技术，获得了可与ＣＭＯＳ结构兼容，基区电阻较小的硅低温双极晶体管。     

硅低温双极晶体管的优化设计与制备──Ⅱ结构与电特性分析

本文在前文器件掺杂分布优化设计的基础上，实现了结构设计和工艺选择，采用多晶硅发射极技术，研制成功了７７Ｋ下高增益（Ｈ＿（ＦＥ）可达２５０）硅双极晶体管；采用多晶硅发射区和基区重掺杂技术，获得了可与ＣＭＯＳ结构兼容，基区电阻较小的硅低温双极晶体管。     

低温基区轻掺杂硅双极晶体管的温度比例因子设计规则

通过对电流增益温度模型的分析，表明发射区重掺杂引起的禁带变窄效应是低温下双极晶体管电流增益衰变的主要原因，提出了用温度比例因子设计低温基区轻掺杂双极晶体管的新设计方法，计算机模拟表明结果良好。     

低温下双极型晶体管电流增益和基区杂质浓度的新关系

<正>近年来,低温(77K)微电子器件和电路的研究得到了国际上广泛重视,已成为半导体学科十分重要和活跃的领域之一.本文建立了低温下双极型晶体管电流增益和基区杂质浓度的新关系,这将成为低温双极型晶体管设计的重要理论依据.以n~+pn型晶体管为例进行分析,当基区杂质浓度N_B小于N_0=1×10~(17)cm~(-3)时,基区中无禁带变窄效应的存在,此时电流增益H_(FE)将随基区杂质浓度N_B上升而下降.     

硅双极晶体管直流特性低温效应的研究

从理论和实验上研究了硅双极晶体管直流特性的低温效应,建立了不同发射结结深的硅双极晶体管电流增益的温度模型,讨论了不同工作电流下H_(FE)的温度特性,并分析了大电流下基区展宽效应的温度关系。     

低导通电压的收集极朝上的Ge／GaAs异质结双极晶体管

低导通电压的收集极朝上的Ｇｅ／ＧａＡｓ异质结双极晶体管日本ＮＴＴ研究所最近报道了一种收集极朝上的Ｇｅ／ＧａＡｓ异质结双极晶体管，这种晶体管能满足高频低功耗工作的要求。通过采用重掺杂Ｂ的Ｇｅ基区和新开发的自对准工艺，降低了基区电阻和寄生参量，其本征基区...     

低温高注入硅双极晶体管电流增益的定量模拟

本文考虑了基区复合电流，发射结空间电荷区复合电流，基区高注入引起的禁带变窄效应，Ｅａｒｌｙ效应，基区和发射区电导调制效应，有效基区展宽效应以及发射区电流集边效应，定量地模拟了硅双极晶体管电流增益在７７Ｋ和３００Ｋ时与集电极电流的关系，并且与实验结果相吻合，计算还表明在低温７７Ｋ时，电流增益的大注入效应由基区电导调制效应和发射区电流集边效应决定，而在３００Ｋ时则由有效基区展宽效应决定。     

Frequency response of advanced silicon bipolar transistors at lowtemperature

The high-frequency behavior of advanced bipolar silicon transistors has been measured at temperatures between 83 and 350 K. The cutoff frequency, DC gain, and associated frequency-dependent parameters are reported. Although the transistors are optimized for room-temperature operation, their performance at liquid-nitrogen temperature is not severely degraded. Though decreased, the current gain remains sufficiently high for use in some applications. The cutoff frequency is reduced by about a factor of two. It is suggested that this is primarily due to an increase of the base transit time and that increasing the base doping may improve the low-temperature response. Using the maximum frequency of oscillation to predict circuit switching speed, it appears that small, high-performance transistors suffer a speed degradation at near liquid-nitrogen temperature     

Non-ideal base current in bipolar transistors at low temperatures

Bipolar transistors havetraditionally been considered not useful in low-temperature applications. This assumption, however, is based upon an incomplete physical understanding of bipolar device physics at low temperatures. This paper shows experimentally that recombination mechanisms play a substantially larger role in determining base current at low temperatures than at room temperature. The results are explained and quantitatively modeled using conventional Shockley-Read-Hall theory, with the addition of the Poole-Frenkel high field effect. It is concluded that trap levels in the silicon bandgap due to bulk traps or interface states are very important in determining bipolar transistor base currents at low temperatures. Non-ideality factors larger than 2 are often observed. Such trap levels will have to be carefully controlled if low-temperature operation of bipolar transistors is to be considered.     

An epitaxial emitter-cap SiGe-base bipolar technology optimized forliquid-nitrogen temperature operation

We give the first demonstration that a properly designed silicon bipolar technology can achieve faster unloaded circuit speed at liquid-nitrogen temperature than at room temperature. Transistors were fabricated using a reduced-temperature process employing an in situ arsenic-doped polysilicon emitter contact, a lightly phosphorus-doped epitaxial emitter-cap layer, and a graded SiGe base. At 84 K, transistors have a current gain of 500, with a cutoff frequency of 61 GHz, and a maximum oscillation frequency of 50 GHz. ECL circuits switch at a record 21.9 ps at 84 K, 3.5-ps faster than at room temperature. Circuits which were optimized for low-power operation achieve a minimum power-delay product of 61 fJ (41.3 ps at 1.47 mW), nearly a factor of two smaller than the best achieved to date at 84 K. The unprecedented performance of these transistors suggests that SiGe-base bipolar technology is a promising candidate for cryogenic applications requiring the fastest possible devices together with the processing maturity and integration level achievable with silicon fabrication     

Electrical characterization of junctions and bipolar transistorsformed with in situ doped low-temperature (800°C) epitaxial silicon

The results of characterization of junctions and bipolar transistors formed with in situ doped low-temperature (800°C) epitaxial silicon are presented. The epitaxial silicon layers were deposited by ultra-low pressure chemical vapor deposition (U-LPCVD) preceded by an in situ Ar sputter clean, which makes possible 800°C fabrication of bipolar transistors. For emitter layer depositions, the U-LPCVD process was plasma enhanced to attain high donor incorporation. Three typical structures of bipolar transistors (A: with epitaxial collector, base, and emitter; B: with epitaxial base and emitter; and C: with epitaxial base) were fabricated and compared in this study. The junction characteristics of the fabricated transistors were also investigated. Functional transistors were obtained for all three structures. Ideality factor of the junctions formed within the epitaxial silicon were near unity (1.01). These results support the claim that the bulk quality of the low-temperature epitaxial silicon is good enough for device application     

A comparison of radiation tolerance of field effect and bipolar transistors

An analytical comparison of the radiation tolerance of conventional silicon field effect transistors and of silicon bipolar transistors has been performed. The channel or base thickness has been used as the respective critical variable, since it measures the degree of difficulty of device fabrication. For field effect transistors, the pinch-off voltage has been used as a free parameter. Based on recent lifetime degradation data for bipolar transistors and on carrier removal data for material of variable resistivity, it is shown that field effect transistors are not inherently more radiation tolerant than bipolar transistors. Only field effect transistors with pinch-off voltages well in excess of 10 volts appear superior to bipolar transistors.     

工作在液氮温度下的低频低噪声双极晶体管的研究

对双极晶体管的低温物理模型和低频噪声模型进行了研究，认为低温下硅双极晶体管电流增益下降的主要原因是低温下非理想基极电流的增加。同时指出，低温下硅双极晶体管１／ｆ噪声的增大，是由于低温下电流增益的减小和载流子在体内和表面的复合增加。通过优化设计，做出了一种低温、低频、低噪声硅双极晶体管。测试表明，在室温（３００Ｋ）下，电流增益、低频转折频率、１ｋＨｚ点的噪声电压分别为β≥８００，ｆ＿Ｌ≤３０Ｈｚ，Ｅｎ（１ｋＨｚ）≤１．５ｎＶ／　　；低温（７７Ｋ）下，电流增益、低频转折频率、１ｋＨｚ点的噪声电压分别为β≥３０，ｆ＿Ｌ≤３００Ｈｚ，Ｅｎ（１ｋＨｚ）≤１．２ｎＶ／。     

Optimization of silicon bipolar transistors for high current gainat low temperatures

Bipolar transistors designed specifically for operation at liquid-nitrogen (LN₂) temperature are discussed. It is found that for high-gain LN₂ bipolar transistors, the emitter concentration should be around 5×10¹⁸ cm^-3. Compensating impurities in the base should be kept to minimum. Test bipolar transistors with polysilicon emitter contacts were fabricated using these criteria. The devices show very little current degradation between room temperature and 77 k. Polysilicon emitter contacts are also shown to be somewhat more effective at lower temperatures