异质结耗尽层基区侧复合对突变HBT重要性分析

基于热场发射.扩散载流子输运模型,在电流连续性方程中包含异质结(BB结)耗尽层基区侧复合电流的前提下,推导出了描述突变HBT电流特性的新解析方程.在此基础上,探讨了对BB结耗尽层基区侧复合电流各不同考虑情况下的HBT电流计算结果的差异程度.结果表明:在较高集电极电流密度处,E-B结耗尽层基区侧的复合电流很重要;此外,在电流连续性方程中包含E-B结耗尽层基区侧的复合电流,这在更高集电极电流密度处也是必要的.     

SiGe HBT直流电流增益模型研究

基于器件结构特点和电学特性,研究了影响SiGe HBT(异质结双极晶体管)直流电流增益的主要因素,分析了不同的电流密度条件下,器件的物理参数、结构参数与集电极电流密度和中性基区复合电流的关系,建立了SiGe HBT集电极电流密度,空穴反注入电流密度、中性基区复合电流、SRH(Shockley-Read- Hall)复合电流密度、俄歇复合电流密度以及直流电流增益模型,对直流电流增益模型进行了模拟仿真,分析了器件物理、结构参数以及复合电流与直流电流增益的关系,得到了SiGe HBT直流电流增益特性的优化理论依据.     

基区重掺杂对SiGe HBT热学性能的影响

相对于同质结晶体管,异质结双极晶体管(HBT)由于异质结的存在,电流增益不再主要由发射区和基区掺杂浓度比来决定,因此可以通过增加基区掺杂浓度来降低基区电阻,提高频率响应,降低噪声系数,但基区掺杂浓度对器件热特性影响的研究却很少。以多指SiGeHBT的热电反馈模型为基础,利用自洽迭代法分析了基区重掺杂对器件集电极电流密度和发射极指温度的影响。通过研究发现,随着基区浓度的增加,SiGe HBT将发生禁带宽度变窄,基区反向注入发射区的空穴电流增大;同时,基区少子俄歇复合增强,这些都将减小集电极电流密度,降低发射极指温度,从而抑制发射极指热电正反馈,提高器件的热稳定性。     

Si／Si1—xGex／Si异质结双极晶体管中基区杂质外扩散与未掺杂Si1—xGex结隔离层

研究了Si/Si1-xGex/Si n-p-n异质结双极晶体管（HBT）的结界面处基区杂质外扩散与标定的未掺杂Si1-xGex隔离层的影响，发现，来自重掺杂基区或非突变界面处少量硼的外扩散会在导带中形成寄生势垒，它严重地影响了HBT中集电极电流的提高，未掺杂界面隔离层能消防这些寄生势垒从而极大地提高了集电极电流。     

si/Si_(1-x)Ge_x/Si异质结双极晶体管中基区杂质外扩散与未掺杂Si_(1-x)Ge_x结隔离层的影响

研究了Si/Si_(1-x)Ge_x/Si n-p-n异质结双极晶体管(HBT)的结界面处基区杂质外扩散与标定的未掺杂Si_(1-x)Ge_x隔离层的影响。发现,来自重掺杂基区或非突变界面处少量硼的外扩散会在导带中形成寄生势垒,它严重地影响了HBT中集电极电流的提高。未掺杂界面隔离层能消除这些寄生势垒从而极大地提高了集电极电流。     

发射极-基极-发射极结构PNP型AlGaAs/GaAs HBT电流增益的理论分析

建立了PNP型异质结双极晶体管基区少数载流子浓度的解析模型.理论分析了发射极-基极-发射极布局的PNP型HBT的电流增益.讨论了不同基极电流成分,如外基区表面复合电流,基极接触处的界面复合电流,基区体内复合电流,以及刻蚀台面处的台面复合电流对电流增益的影响.     

发射极-基极-发射极结构PNP型AlGaAs/GaAsHBT电流增益的理论分析

建立了 PNP型异质结双极晶体管基区少数载流子浓度的解析模型 .理论分析了发射极 -基极 -发射极布局的PNP型 HBT的电流增益 .讨论了不同基极电流成分 ,如外基区表面复合电流 ,基极接触处的界面复合电流 ,基区体内复合电流 ,以及刻蚀台面处的台面复合电流对电流增益的影响     

基区复合对nSi/pSi_(1-x)Ge_x/nSi晶体管共射极电流增益的影响

采用二维数值模拟方法详细分析了基区复合电流对nSi/pSi1-xGex/nSi应变基区异质结双极晶体管(HBT)共射极电流放大系数β的影响,给出了Si1-xGexHBT的Gummel图、平衡能带图.得出在靠近发射结附近基区的复合电流是引起β下降的主要因素,并给出了减小基区复合电流的Ge分布形式.     

异质结双极晶体管基区复合电流的解析模型

从求解异质结双极晶体管基区的二维电流连续性方程出发，推导出了基区少数载流子浓度的解析解，由此获得了基区各处复合电流的解析表达式。基于该模型完成了算法研究和软件编制，计算出了器件所能达到理论电流增益。     

新型恒压控制型负阻HBT的研制进展

研究了HBT产生负阻的可能机制,通过对材料结构和器件结构的特殊设计,采用常规台面HBT工艺,先后研制出3类高电流峰谷比的恒压控制型负阻HBT.超薄基区HBT的负阻特性是由超薄基区串联电阻压降调制效应造成的,在GaAs基InGaP/GaAs和AlGaAs/GaAs体系DHBT中均得到了验证.双基区和电阻栅型负阻HBT均为复合型负阻器件.双基区负阻HBT通过刻断基区,电阻栅负阻HBT通过在集电区制作基极金属形成集电区反型层,构成纵向npn与横向pnp的复合结构,由反馈结构(pnp)的集电极电流来控制主结构(npn)的基极电流从而产生负阻特性.3类负阻HBT与常规HBT在结构和工艺上兼容,兼具HBT的高速高频特性和负阻器件的双稳、自锁、节省器件的优点.     

异质结双极晶体管基区复合电流的解析模型

从求解异质结双极晶体管基区的二维电流连续性方程出发，推导出了基区少数载流子浓度的解析解，由此获得了基区各种复合电流的解析表达式。基于该模型完成了算法研究和软件编制，计算出了器件所能达到的理论电流增益。     

Effect of bulk recombination current on the current gain ofGaAs/AlGaAs heterojunction bipolar transistors in GaAs-on-Si

The effect of bulk recombination current on the current gain of heterojunction bipolar transistors (HBTs) in GaAs-on-Si has been studied. A thin AlGaAs emitter layer is used to prevent an exposed extrinsic base region, which has previously masked the effect of the bulk recombination current on the current gain in HBTs. It is found that once the surface recombination current is removed, the current grain due to bulk recombination alone is approximately ten times lower for the HBTs in GaAs-on-Si than for HBTs in GaAs. The difference in the current gain is probably due to electrically active dislocations in the base in the HBTs in GaAs-on-Si, where the density is about 10⁸ cm^-2 as measured by transmission electron microscopy     

A new physical model of the light amplifying optical switch (LAGS)

A new physical model of determining the static I-V curve of the light amplifying optical switch (LAOS) is derived. The model is based on deriving the currents of the HPT and the feedback current of the LAOS. The feedback currents for optical and/or electrical feedback are determined by solving the continuity equation in the collector and the base of the HPT. A negative resistance region in the I-V curve is obtained and controlled by varying the feedback coefficient of the device and the Early effect coefficient. The main factors affecting the negative resistance region are the feedback coefficient, Early effect, the recombination currents in the emitter-base space-charge region, and the ratio of the collector to base doping. The switching voltage of the device is also calculated for different parameters     

Space-charge region recombination in heterojunction bipolartransistors

A new comprehensive model for space-charge region (SCR) recombination current in abrupt and graded energy gap heterojunction bipolar transistors (HBTs) is derived. It is shown that if a spike is present in one of the bands at the heterojunction interface, the SCR recombination current becomes interrelated with the collector current. A previously proposed charge control model for the HBT is modified to include the SCR recombination current. The model is used to study SCR recombination characteristics in HBTs     

The importance of bandgap narrowing distribution between theconduction and valence bands in abrupt HBTs

Abrupt heterojunction bipolar transistors (HBTs) show interfaces where discontinuities in the energy levels appear. Currents through these interfaces are controlled by tunneling and thermionic emission. The values of these currents depend on the form and height of the energy barriers, which are disturbed by the heavy doping effects on semiconductor energy band structure. In this work, the real bandgap narrowing is distributed between the conduction and valence bands according to Jain-Roulston model, and its effect on the base and collector currents of Si/SiGe and InP/InGaAs HBTs is analyzed. This analysis is carried out through a numerical model which combines the drift-diffusion transport in the bulk of transistor with the thermionic emission and tunneling at the base-emitter interface, and an empirically determined surface recombination current     

半导体中非平衡载流子的输运过程(Ⅰ)

在描述载流子输运过程的玻尔兹曼方程的碰撞项中考虑了带间跃迁的贡献,从而将它推广到存在非平衡载流子的情况。由此导出了非平衡载流子寿命,复合几率的统计表达式,以及包括产生-复合过程的电荷连续性方程和稳态输运过程的电流方程。     

1/f noise in n-p-n GaAs/AlGaAs heterojunction bipolartransistors:iImpact of intrinsic transistor and parasitic seriesresistances

1/f noise experiments were performed for n-p-n GaAs/AlGaAs HBTs as a function of forward bias at room temperature. The experimental data are discussed with the help of new expressions for the 1/f noise in bipolar transistors where the influence of internal parasitic series resistances has been taken into account. At low forward currents the 1/f noise is determined by spontaneous fluctuations in the base and collector currents. At fixed bias, the collector current noise exceeds the base current noise. At higher forward currents the parasitic series resistances and their 1/f noise become important. Experimental results from the literature are compared with the results     

High-gain InGaAlAs/InGaAs heterojunction bipolar transistors andphototransistors

The characteristics of InGaAlAs/InGaAs heterojunction bipolar transistors (HBTs) grown by molecular beam epitaxy are described. A current gain of 15600 at a current density of ~10⁴ A/cm² and an emitter-base heterojunction ideality factor of 1.02 were measured. Appropriately designed InGaAlAs/InGaAs HBTs, when operated as phototransistors, also had high gains. A current gain of 1000 for a collector current of only 10 μA was obtained for phototransistors. Such high gains are due to low recombination currents as a consequence of the good crystalline quality of the InGaAlAs bulk and InGaAlAs/InGaAs interface     

Experimental comparison of base recombination currents in abrupt and graded AlGaAs/GaAs heterojunction bipolar transistors

The relative importance of the base bulk recombination current and the base-emitter junction space charge recombination current is examined for AlGaAs/GaAs HBTs with different grading schemes in the base-emitter junction. Experimental results demonstrate that, in abrupt HBTs, the base bulk recombination current is larger, and the base current increases with the base-emitter bias with an ideality factor of approximately 1. In contrast, in graded HBTs, the space charge recombination current dominates and the base current ideality factor is approximately 2. These experimental results agree well with a published theoretical calculation.<>     

Surface-recombination-free InGaAs/InP HBTs and the base contact recombination

Surface-recombination-free InGaAs/InP HBTs with graded base have been demonstrated. The HBTs were passivated by ammonium sulfide. The current gain of the nonself-aligned HBTs was independent of the emitter periphery, indicating that the surface recombination was removed by the passivation. For the self-aligned HBTs, the current gain was still dependent on the emitter periphery after the passivation due to the base contact recombination. A surface leakage channel has been identified to result in a significant increase in the base contact recombination. The passivation has two effects: one is the surface recombination velocity reduction and the other is the surface leakage channel elimination.