A novel 4H-SiC lateral bipolar junction transistor structure with high voltage and high current gain

In this paper, a novel structure of a 4H-SiC lateral bipolar junction transistor (LBJT) with a base field plate and double RESURF in the drift region is presented. Collector-base junction depletion extension in the base region is restricted by the base field plate. Thin base as well as low base doping of the LBJT therefore can be achieved under the condition of avalanche breakdown. Simulation results show that thin base of 0.32 μm and base doping of 3×1017 cm-3 are obtained, and corresponding current gain is as high as 247 with avalanche breakdown voltage of 3309 V when the drift region length is 30 μm. Besides, an investigation of a 4H-SiC vertical BJT (VBJT) with comparable breakdown voltage (3357 V) shows that the minimum base width of 0.25 μm and base doping as high as 8×1017 cm-3 contribute to a maximum current gain of only 128.     

超结硅锗碳异质结双极晶体管机理研究与特性分析优化

提出一种超结硅锗碳异质结双极晶体管(SiGeC HBT)新结构.详细分析了新结构中SiGeC基区和超结结构的引入对器件性能的影响,并对其电流输运机制进行研究.基于SiGeC/Si异质结技术,新结构器件的高频特性优良;同时超结结构的存在,在集电区内部水平方向和垂直方向都建立了电场,二维方向上的电场分布相互作用大大提高了新结构器件的耐压能力.结果表明:超结SiGeC HBT与普通结构SiGeC HBT相比,击穿电压提高了48.8%;更重要的是SiGeC HBT器件中超结结构的引入,不会改变器件高电流增益、高频率特性的优点;新结构器件与相同结构参数的Si双极晶体管相比,电流增益提高了10.7倍,截止频率和最高震荡频率也得到了大幅度改善,很好地实现了高电流增益、高频率特性和高击穿电压三者之间的折中.对超结区域的柱区层数和宽度进行优化设计,随着柱区层数的增多,击穿电压显著增大,电流增益有所提高,截止频率和最高震荡频率减低,但幅度很小.综合考虑认为超结区域采用pnpn四层结构是合理的.     

不同顺序中子/γ辐照对双极器件电流增益的影响

利用CFBR-Ⅱ快中子反应堆（中国第二座快中子脉冲堆）和⁶⁰Co装置开展不同顺序的中子/γ辐照双极晶体管的实验。在集电极-发射极电压恒定条件下,测量了双极晶体管电流增益随集电极电流的变化曲线,研究不同顺序中子/γ辐照对双极晶体管电流增益的影响。分析实验结果发现,集电极-发射极电压一定时,集电极电流极低情况下电流增益退化比较大,随集电极电流增加电流增益逐渐减小;就实验选中的两类晶体管而言,先中子后γ辐照造成双极晶体管电流增益的退化程度大于先γ后中子辐照,而且PNP型晶体管比NPN型晶体管差异更明显。本文进行了双极晶体管电离/位移协同辐照效应相关机理的初步探讨。     

Fabrication and characterization of 4H—SiC bipolar junction transistor with double base epilayer

In this paper we report on a novel structure of a 4H-SiC bipolar junction transistor with a double base epilayer that is continuously grown.The measured dc common-emitter current gain is 16.8 at IC = 28.6 mA(J C = 183.4 A/cm2),and it increases with the collector current density increasing.The specific on-state resistance(Rsp-on) is32.3mΩ·cm 2 and the open-base breakdown voltage reaches 410 V.The emitter N-type specific contact resistance and N + emitter layer sheet resistance are 1.7×10-3 Ω·cm2 and 150 /,respectively.     

双极型晶体管损坏与强电磁脉冲注入位置的关系

利用时域有限差分法,对双极型晶体管(BJT)在强电磁脉冲作用下的瞬态响应进行了2维数值模拟,研究了电磁脉冲从不同极板注入时BJT的响应情况,根据温度分布的集中程度分析了发生烧毁的难易程度。模拟得出：发射极注入最容易导致烧毁,集电极注入次之,基极注入相对不易导致烧毁;发射极注入烧毁所消耗能量随着脉冲电压上升而下降,到30 V以后基本与电压的升高无关,集电极注入烧毁所消耗的能量则随着电压上升而上升,到100 V以后由于BE结上热点的出现而开始下降。     

A novel structure of a high current gain 4H-SiC BJT with a buried layer in base

In this paper, a new structure of a 4H-SiC bipolar junction transistor (BJT) with a buried layer (BL) in the base is presented. The current gain shows an approximately 100% increase compared with that of the conventional structure. This is attributed to the creation of a built-in electric field for the minority carriers to transport in the base which is explained based on 2D device simulations. The optimized design of the buried layer region is also considered by numeric simulations.     

含有本征SiGe层的SiGe异质结双极晶体管集电结耗尽层宽度模型

本文分别建立了含有本征SiGe层的SiGe HBT(异质结双极晶体管)集电结耗尽层各区域的电势、电场分布模型,并在此基础上,建立了集电结耗尽层宽度和延迟时间模型,对该模型进行了模拟仿真,定量地分析了SiGe HBT物理、电学参数对集电结耗尽层宽度和延迟时间的影响,随着基区掺杂浓度和集电结反偏电压的提高,集电结耗尽层延迟时间也随之增大,而随着集电区掺杂浓度的提高和基区Ge组分增加,集电结耗尽层延迟时间随之减小. 关键词： SiGe HBT 集电结耗尽层 延迟时间     

Thermal stability improvement of a multiple finger power SiGe heterojunction bipolar transistor under different power dissipations using non-uniform finger spacing

A method of non-uniform finger spacing is proposed to enhance thermal stability of a multiple finger power SiGe heterojunction bipolar transistor under different power dissipations. Temperature distribution on the emitter fingers of a multi-finger SiGe heterojunction bipolar transistor is studied using a numerical electro-thermal model. The results show that the SiGe heterojunction bipolar transistor with non-uniform finger spacing has a small temperature difference between fingers compared with a traditional uniform finger spacing heterojunction bipolar transistor at the same power dissipation. What is most important is that the ability to improve temperature non-uniformity is not weakened as power dissipation increases. So the method of non-uniform finger spacing is very effective in enhancing the thermal stability and the power handing capability of power device. Experimental results verify our conclusions.     

InGaZnO薄膜晶体管泄漏电流模型

研究了非晶氧化锌镓铟薄膜晶体管(amorphous InGaZnO thin-film transistor,InGaZnO TFT)的泄漏电流模型.基于Poole-Frenkel热发射效应和热离子场致发射效应的泄漏电流产生机制,分别得到了高电场和低电场条件下的载流子产生-复合率.在此基础上推导得到了InGaZnO TFT的分段式泄漏电流-电压数学模型,并利用平滑函数得到了关断区和亚阈区连续统一的泄漏电流模型.所提出的泄漏电流模型的计算值和TCAD模拟值与实验结果较为吻合.利用所提出的InGaZnO TFT泄漏电流模型和TCAD模拟,讨论了InGaZnO TFT不同的沟道宽度、沟道长度和栅介质层厚度对泄漏电流值的影响.研究结果对InGaZnO TFT集成传感电路的设计具有一定参考价值.     

双极型晶体管在强电磁脉冲作用下的瞬态响应

 利用时域有限差分法,对双极型晶体管在强电磁脉冲作用下的瞬态响应进行了2维数值模拟,分析了器件烧毁过程中电场、电流密度、温度等参数的分布及变化情况,分别观察了低电压和高电压脉冲作用下烧毁过程中热点的形成过程,并得到了器件烧毁所需时间以及能量与脉冲电压幅度之间的关系。在电压脉冲较低时,烧毁点位于通道中靠近集电极的位置,当脉冲电压达到一定幅度的时候,由于发射极与集电极之间发生雪崩击穿,基极和发射极之间电势会抬高,从而引起基极和发射极之间的击穿,形成新的热点,并在电压幅度约高于100 V的情况下会率先达到烧毁温度。随着脉冲电压幅度的增高,晶体管烧毁所需时间呈负指数减少,而所需能量在55~100 V之间接近于线性增长,直到电压幅度约高于100 V时才开始减少。     

伽玛辐照对SiGe异质结双极型晶体管的集电极电流和厄尔利电压的影响

研究了伽玛辐照效应对SiGe异质结双极型晶体管的集电极电流和厄尔利电压的影响。经过104 Gy的伽玛总剂量辐照后,集电极电流和厄尔利电压均增加。另外,辐照后发射结和极电结的开启电压和击穿电压也均有一定程度的减小。以上这些变化均是由于辐照产生的缺陷引起发射区和集电区有效掺杂浓度减小所致。     

伽玛辐照对SiGe异质结双极型晶体管的集电极电流和厄尔利电压的影响

 研究了伽玛辐照效应对SiGe异质结双极型晶体管的集电极电流和厄尔利电压的影响。经过10⁴ Gy的伽玛总剂量辐照后,集电极电流和厄尔利电压均增加。另外,辐照后发射结和极电结的开启电压和击穿电压也均有一定程度的减小。以上这些变化均是由于辐照产生的缺陷引起发射区和集电区有效掺杂浓度减小所致。     

双极型晶体管损坏与强电磁脉冲注入位置的关系

 利用时域有限差分法,对双极型晶体管(BJT)在强电磁脉冲作用下的瞬态响应进行了2维数值模拟,研究了电磁脉冲从不同极板注入时BJT的响应情况,根据温度分布的集中程度分析了发生烧毁的难易程度。模拟得出：发射极注入最容易导致烧毁,集电极注入次之,基极注入相对不易导致烧毁;发射极注入烧毁所消耗能量随着脉冲电压上升而下降,到30 V以后基本与电压的升高无关,集电极注入烧毁所消耗的能量则随着电压上升而上升,到100 V以后由于BE结上热点的出现而开始下降。     

采用发射极非均匀指间距技术改善功率异质结双极晶体管热稳定性的研究

为了提高多发射极功率异质结双极晶体管的热稳定性,本文利用耦合热阻表征发射极指间距变化对发射极指间热耦合作用的影响,得到了耦合热阻与发射极指间距之间的变化关系,提出了发射极非均匀指间距技术.通过热电反馈模型对采用发射极非均匀指间距技术的功率HBT进行热稳定性分析,得到了多发射极指上的温度分布.结果表明,多发射极HBT在采用非均匀发射极指间距技术后,峰值温度明显下降,温度变化幅度更加平缓,有效地提高了器件的热稳定性. 关键词： 异质结双极晶体管 耦合热阻 指间距     

双极结型晶体管的集电结反向雪崩击穿特性

通过气体放电产生更高浓度的低温等离子体要求具有纳秒上升沿和纳秒脉宽的高重频快脉冲,而目前被广泛使用的MOSFET和IGBT都无法满足这些参数要求,而双极结型晶体管(BJT）的集电极与发射极之间的雪崩击穿过程具有快导通、快恢复、高稳定性等优点,适合作为小型Marx发生器的自击穿开关。文中对用多种型号的BJT进行击穿特性比较测试实验,发现可以通过改变BJT的门极和发射极的并联电阻来调节其雪崩击穿电压,实现一定范围的工作电压。雪崩击穿恢复特性实验表明,当击穿电流衰减到低于维持电流时,BJT就会开始恢复绝缘而关断,通过改变电路中的参数以控制击穿电流的变化就可以控制BJT的雪崩击穿导通时间（即导通脉宽）。将这些结论应用到实际电路中,可获得上升沿5 ns、脉宽为10 ns、幅值2 kV、重复频率高达100 kHz的纳秒快脉冲,可用于激发高浓度低温等离子体。     

Physical processes of current gain in InAs bipolar junction transistors

InAs bipolar junction transistors (BJTs), grown by molecular beam epitaxy, are reported with common emitter current gains (β's) as large as 400. The factors affecting the common emitter current gain have been studied by estimating the magnitudes of the base transport factor (α_T) and emitter injection efficiency (γ). This has been accomplished by studying a sequence of InAs BJTs with varying emitter doping densities, N_E. Minority carrier diffusion length in the base (L_B), α_T, and γ have been extracted from measured electrical characteristics. The results of the study of these InAs BJTs are as follows: L_B≈0.4 μm, α_T≈98% and γ ranges from 92% to nearly 100% depending on N_E. This knowledge of the magnitudes of the injection efficiencies suggests when it would be useful to move from the simple BJT structure to the more advanced heterojunction bipolar transistor (HBT) structure. Lower γ BJTs would be improved, however high-γ BJTs would benefit little, by the use of the widegap emitters of HBTs. The method developed here to estimate γ, α_T and L_B is not specific to InAs BJTs, but should be useful for study of BJTs and HBTs in any material system.     

A device model for thin silicon-on-insulator SiGe heterojunction bipolar transistors with saturation effects

In this paper, we describe the saturation effect of a silicon germanium (SiGe) heterojunction bipolar transistor (HBT) fabricated on a thin silicon-on-insulator (SOI) with a step-by-step derivation of the model formulation. The collector injection width, the internal base—collector bias, and the hole density at the base—collector junction interface are analysed by considering the unique features of the internal and the external parts of the collector, as they are different from those of a bulk counterpart.     

Thermal resistance matrix representation of thermal effects and thermal design in multi-finger power heterojunction bipolar transistors

The thermal resistance matrix including self-heating thermal resistance and thermal coupling resistance is presented to describe the thermal effects of multi-finger power heterojunction bipolar transistors. The dependence of thermal resistance matrix on finger spacing is also investigated. It is shown that both self-heating thermal resistance and thermal coupling resistance are lowered by increasing the finger spacing, in which the downward dissipated heat path is widened and the heat flow from adjacent fingers is effectively suppressed. The decrease of self-heating thermal resistance and thermal coupling resistance is helpful for improving the thermal stability of power devices. Furthermore, with the aid of the thermal resistance matrix, a 10-finger power heterojunction bipolar transistor (HBT) with non-uniform finger spacing is designed for high thermal stability. The optimized structure can effectively lower the peak temperature while maintaining a uniformity of the temperature profile at various biases and thus the device effectively may operate at a higher power level.     

Ge组分分布对基区杂质非均匀分布的SiGe HBT温度特性的影响

众所周知, 双极型晶体管的设计主要是基区的设计. 一般而言, 基区的杂质分布是非均匀的. 本文首先研究了非均匀的杂质高斯分布对器件温度分布、增益和截止频率的温度特性的影响, 发现增益和截止频率具有正温度系数, 体内温度较高. 随后研究了基区Ge组分分布对这些器件参数的影响. 均匀Ge组分分布和梯形Ge组分分布的SiGe 异质结双极型晶体管增益和截止频率具有负温度系数, 具有较好的体内温度分布. 进一步的研究表明, 具有梯形Ge组分分布的SiGe 异质结双极型晶体管, 由于Ge组分缓变引入了少子加速电场, 不但使它的增益和截止频率具有较高的值, 而且保持了较弱的温度敏感性, 在增益、特征频率大小及其温度敏感性、体内温度分布达到了很好的折中.     

Two-dimensional analysis of the interface state effect on current gain for a 4H-SiC bipolar junction transistor

This paper studies two-dimensional analysis of the surface state effect on current gain for a 4H-SiC bipolar junction transistor (BJT).Simulation results indicate the mechanism of current gain degradation,which is surface Fermi level pinning leading to a strong downward bending of the energy bands to form the channel of surface electron recombination current.The experimental results are well-matched with the simulation,which is modeled by exponential distributions of the interface state density replacing the single interface state trap.Furthermore,the simulation reveals that the oxide quality of the base emitter junction interface is very important for 4H-SiC BJT performance.