ELDRS and dose-rate dependence of vertical NPN transistor

The enhanced low-dose-rate sensitivity (ELDRS) and dose-rate dependence of vertical NPN transistors are investigated in this article.The results show that the vertical NPN transistors exhibit more degradation at low dose rate,and that this degradation is attributed to the increase on base current.The oxide trapped positive charge near the SiO2-Si interface and interface traps at the interface can contribute to the increase on base current and the two-stage hydrogen mechanism associated with space charge effect can well explain the experimental results.     

基于1/f噪声的NPN晶体管辐照感生电荷的定量分离

本文针对NPN双极性晶体管, 在研究辐照感生的氧化层电荷及界面态对晶体管基极电流和1/f噪声的影响的基础上, 建立辐照感生氧化层电荷及界面态与基极电流和1/f噪声的定量物理模型. 根据所建立的模型, 提出一种新的分离方法, 利用1/f噪声和表面电流求出氧化层电荷密度, 利用所求得氧化层电荷密度和表面电流求出界面态密度. 利用本方法初步实现了辐照感生氧化层电荷及界面态的定量计算.     

Comparison of effect of 5 MeV proton and Co-60 gamma irradiation on silicon NPN rf power transistors and N–channel depletion MOSFETs

NPN transistors and N-channel depletion metal oxide semiconductor field effect transistors (MOSFETs) were irradiated with 5?MeV protons and ⁶⁰Co gamma radiation in the dose ranging from 1?Mrad(Si) to 100?Mrad(Si). The different electrical characteristics of the NPN transistor such as Gummel characteristics, excess base current (ΔI_B), dc current gain (h_FE), transconductance (g_m), displacement damage factor (K) and output characteristics were studied as a function of total dose. The different electrical characteristics of N-channel MOSFETs such as threshold voltage (V_th), density of interface trapped charges (ΔN_it), density of oxide trapped charges (ΔN_ot), transconductance (g_m), mobility (µ) and drain saturation current (I_DSat) were studied systematically before and after irradiation in the same dose ranges. A considerable increase in the base current (I_B) and decrease in the h_FE, g_m and collector saturation current (I_CSat) were observed after irradiation in the case of the NPN transistor. In the N-channel MOSFETs, the ΔN_it and ΔN_ot were found to increase and V_th, g_m, µ and I_DSat were found to decrease with increase in the radiation dose. The 5?MeV proton irradiation results of both the NPN transistor and N-channel MOSFETs were compared with ⁶⁰Co gamma-irradiated devices in the same dose ranges. It was observed that the degradation in 5?MeV proton-irradiated devices is more when compared with the ⁶⁰Co gamma-irradiated devices at higher total doses.     

Effects of orientation of substrate on the enhanced low-dose-rate sensitivity (ELDRS) in NPN transistors

The radiation effects and annealing characteristics of two types of domestic NPN bipolar junction transistors, fabricated with different orientations, were investigated under different dose-rate irradiation. The experimental results show that both types of the NPN transistors exhibit remarkable Enhanced Low-Dose-Rate Sensitivity (ELDRS). After irradiation at high or low dose rate, the excess base current of NPN transistors obviously increased, and the current gain would degrade rapidly. Moreover, the decrease of collector current was also observed. The NPN transistor with (111) orientation was more sensitive to ionizing radiation than that with (100) orientation. The underlying mechanisms of various experimental phenomena are discussed in detail in this paper.     

Degradation mechanisms of current gain in NPN transistors

An investigation of ionization and displacement damage in silicon NPN bipolar junction transistors (BJTs) is presented. The transistors were irradiated separately with 90-keV electrons, 3-MeV protons and 40-MeV Br ions. Key parameters were measured {\em in-situ} and the change in current gain of the NPN BJTS was obtained at a fixed collector current (I_{\rm c}=1~mA). To characterise the radiation damage of NPN BJTs, the ionizing dose D_{\i} and displacement dose D_{\d} as functions of chip depth in the NPN BJTs were calculated using the SRIM and Geant4 code for protons, electrons and Br ions, respectively. Based on the discussion of the radiation damage equation for current gain, it is clear that the current gain degradation of the NPN BJTs is sensitive to both ionization and displacement damage. The degradation mechanism of the current gain is related to the ratio of D_{\rm d}/(D_{\rm d}+D_{\rm i}) in the sensitive region given by charged particles. The irradiation particles leading to lower D_{\rm d}/(D_{\rm d}+D_{\rm i}) within the same chip depth at a given total dose would mainly produce ionization damage to the NPN BJTs. On the other hand, the charged particles causing larger D_{\rm d}/(D_{\rm d}+D_{\rm i}) at a given total dose would tend to generate displacement damage to the NPN BJTs. The Messenger--Spratt equation could be used to describe the experimental data for the latter case.     

Effect of bias condition on heavy ion radiation in bipolar junction transistors

The characteristic degradations in a silicon NPN bipolar junction transistor(BJT) of 3DG142 type are examined under irradiation with 40-MeV chlorine(Cl) ions under forward,grounded,and reverse bias conditions,respectively.Different electrical parameters are in-situ measured during the exposure under each bias condition.From the experimental data,a larger variation of base current(I B) is observed after irradiation at a given value of base-emitter voltage(V BE),while the collector current is slightly affected by irradiation at a given V BE.The gain degradation is affected mostly by the behaviour of the base current.From the experimental data,the variation of current gain in the case of forward bias is much smaller than that in the other conditions.Moreover,for 3DG142 BJT,the current gain degradation in the case of reverse bias is more severe than that in the grounded case at low fluence,while at high fluence,the gain degradation in the reverse bias case becomes smaller than that in the grounded case.     

Effects of orientation of substrate on the enhanced low-dose-rate sensitivity （ELDRS） in NPN transistors

The radiation effects and annealing characteristics of two types of domestic NPN bipolar junction transistors, fabricated with different orientations, were investigated under different dose-rate irradiation. The experimental results show that both types of the NPN transistors exhibit remarkable Enhanced Low-Dose-Rate Sensitivity (ELDRS). After irradiation at high or low dose rate, the excess base current of NPN transistors obviously increased, and the current gain would degrade rapidly. Moreover, the decrease of collector current was also observed. The NPN transistor with <111> orientation was more sensitive to ionizing radiation than that with <100> orientation. The underlying mechanisms of various experimental phenomena are discussed in detail in this paper.     

Effect of bias condition on heavy ion radiation in bipolar junction transistor

The characteristic degradations in silicon NPN bipolar junction transistor (BJT) of 3DG142 type are examined under the irradiation with 40-MeV chlorine (Cl) ions under forward, grounded, and reverse bias conditions, respectively. Different electrical parameters are in-situ measured during the exposure under each bias condition. From the experimental data, larger variation of base current (I_B) is observed after irradiation at a given value of base-emitter voltage (V_BE), while the collector current is slightly affected by irradiation at a given V_BE. The gain degradation is affected mostly by the behaviour of the base current. From the experimental data, the variation of current gain in the case of forward bias is much smaller than that in the other conditions. Moreover, for 3DG142 BJT, the current gain degradation in the case of reverse bias is more severe than that in the grounded case at low fluence, while at high fluence, the gain degradation in the reverse bias case becomes smaller than that in the grounded case.     

半导体器件总剂量辐射效应的热力学影响

对商用三极管和MOS场效应晶体管进行了不同环境温度下的总剂量辐照实验,对比了不同辐照温度对这两种器件辐射效应特性的影响。实验结果表明,对于同一辐照总剂量,三极管的基极电流、电流增益和MOS场效应晶体管的阈值电压漂移值都随着辐照温度的不同而存在较大的差异。总剂量为100 krad,辐照温度分别为25,70,100 ℃时,NPN三极管的电流增益倍数分别衰减了71,89和113,而NMOS晶体管的阈值电压V_T分别减少了3.53,2.8,2.82 V。     

60Co γ-ray induced gain degradation in bipolar junction transistors

Commercial indigenously made npn and pnp bipolar junction switching transistors used for space applications are investigated for ⁶⁰Co γ-ray induced effects. The on-line as well as off-line measurements indicate that the forward current gain of the transistors decreases significantly as the accumulated dose increases. Excess base current model is employed to account for the current gain degradation. The pnp transistor undergoes as much degradation as the npn type. It is found that bulk degradation by displacement damage is the dominant mechanism leading to reduction in forward current gain of npn transistors. On the other hand it appears that, in addition to bulk damage, surface degradation due to accumulation of interface states at the silicon-silicon dioxide interface also contributes significantly to gain degradation in pnp transistor as evident from thermal annealing studies. Further, estimation reveals that the transistor with larger base width has higher displacement damage factor.     

Si_3N_4钝化层对横向PNP双极晶体管电离辐射损伤的影响机理

航天器中电子器件在轨服役期间,会遭受到空间带电粒子及各种射线的辐射环境的显著影响,易于造成电离辐射损伤.本文采用60Coγ射线辐照源,针对有/无Si_3N_4钝化层结构的横向PNP型(LPNP)双极晶体管,开展了电离辐射损伤效应及机理研究.利用KEITHLEY 4200-SCS半导体参数测试仪测试了LPNP晶体管电性能参数(包括Gummel特性曲线和电流增益等).采用深能级瞬态谱分析仪(DLTS),对辐照前后有/无Si_3N_4钝化层结构的LPNP晶体管的电离缺陷进行测试.研究结果表明,在相同吸收剂量条件下,与无Si_3N_4钝化层的晶体管相比,具有Si_3N_4钝化层的LPNP晶体管基极电流退化程度大,并且随吸收剂量的增加,电流增益退化更为显著.通过DLTS分析表明,与无Si_3N_4钝化层的晶体管相比,有Si_3N_4钝化层的晶体管辐射诱导的界面态能级位置更接近于禁带中心.这是由于制备Si_3N_4钝化层时引入了大量的氢所导致,而氢的存在会促使辐射诱导的界面态能级位置更接近于禁带中心,复合率增大,从而加剧了晶体管性能的退化.     

1 550 nm波长PNP型InGaAsP-InP异质结晶体管激光器材料设计与外延生长

基于器件模拟仿真,设计了一种PNP型1.5 μm 波长多量子阱InGaAsP-InP异质结晶体管激光器材料外延结构,并采用金属有机化学气相沉积外延生长.其中基区采用N型Si掺杂.因为扩散系数小,比较P型Zn搀杂具有较高的稳定性,因而较NPN结构外延材料容易获得高质量的光学有源区.由于N型欧姆接触比P型容易获得,基区搀杂浓度可以相对较低,有利于减小基区光损耗和载流子复合,从而获得较低的阈值电流和较高的输出光功率.所获得的外延材料呈现较高光-荧光谱峰值和65.1 nm较低半峰宽.测试结果显示了较高的外延片光学质量.     

Comparison of 1 MeV electron,Co-60 gamma and 1 MeV proton irradiation effects on silicon NPN transistors

The total dose effects of 1?MeV electrons on the dc electrical characteristics of silicon NPN transistors are investigated in the dose range from 100?krad to 100?Mrad. The different electrical characteristics such as Gummel characteristics, excess base current (ΔI_B), dc current gain (h_FE), transconductance (g_m), displacement damage factor (K) and output characteristics were studied in situ as a function of total dose. A considerable increase in base current (I_B) and a decrease in h_FE, g_m and I_CSat was observed after 1?MeV electron irradiation. The collector–base (C–B) junction capacitance of transistors was measured to estimate the change in the effective carrier concentration. After 1?MeV electron irradiation, a considerable degradation in capacitance was observed. The plot of (1/C²) versus voltage shows that the effective carrier concentration and built-in voltage (V_bi) increase marginally upon 1?MeV electron irradiation. The results of 1?MeV electron irradiation were compared with 1?MeV proton and Co-60 gamma irradiation results in the same dose range. The degradation for 1?MeV electron and Co-60 gamma-irradiated transistors was significantly less when compared to 1?MeV proton-irradiated transistor. The 1?MeV proton, 1?MeV electron and Co-60 gamma-irradiated transistors were subjected to isochronal annealing to analyze the recovery of the electrical parameters.     

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。     

Two-dimensional analysis of the interface states effects on current gain for 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.     

Design and investigation of novel ultra-high-voltage junction field-effect transistor embedded with NPN

Ultra-high-voltage(UHV) junction field-effect transistors(JFETs) embedded separately with the lateral NPN(JFETLNPN), and the lateral and vertical NPN(JFET-LVNPN), are demonstrated experimentally for improving the electrostatic discharge(ESD) robustness. The ESD characteristics show that both JFET-LNPN and JFET-LVNPN can pass the 5.5-k V human body model(HBM) test. The JFETs embedded with different NPNs have 3.75 times stronger in ESD robustness than the conventional JFET. The failure analysis of the devices is performed with scanning electron microscopy, and the obtained delayer images illustrate that the JFETs embedded with NPN transistors have good voltage endurance capabilities. Finally,the internal physical mechanism of the JFETs embedded with different NPNs is investigated with emission microscopy and Sentaurus simulation, and the results confirm that the JFET-LVNPN has stronger ESD robustness than the JFET-LNPN,because the vertical NPN has a better electron collecting capacity. The JFET-LVNPN is helpful in providing a strong ESD protection and functions for a power device.     

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.     

带有n+深阱的三阱CMOS工艺中寄生NPN双极效应及其对电荷共享的影响

基于三维TCAD器件模拟, 研究了带有 n⁺深阱的90 nm三阱CMOS器件在重离子辐照下产生的电荷共享效应. 研究结果表明在重离子辐照时, n⁺深阱会导致寄生的NPN双极型晶体管触发, 显著增强NMOS间的电荷共享, 其放大因子达到双阱工艺中寄生PNP晶体管放大因子的2---4倍. 进而分别研究了n阱接触和p 阱接触对寄生NPN双极放大的影响, 结果表明增大p阱接触的面积和减小 n 阱接触的距离将抑制NPN晶体管的放大作用, 而增大n 阱接触的面积将增强NPN的放大作用.     

InP-based deep-ridge NPN transistor laser

We report an InP-based deep-ridge NPN transistor laser (TL, λ～1.5 μm). By placing the quantum well (QW) active material above the heavily Zn-doped base layer, both the optical absorption of the heavily p-doped base material and the damage of the quality of the QWs resulted from the Zn diffusion into the QWs are decreased greatly. CW operation of the TL is achieved at -40 °C, which is much better than the shallow-ridge InP-based NPN TL. With future optimization of the growth procedure, significant improvement of the performance of the deep-ridge InP-based NPN TLs is expected.     

Radiation-induced 1/f noise degradation of PNP bipolar junction transistors at different dose rates

It is found that ionizing-radiation can lead to the base current and the 1/f noise degradations in PNP bipolar junction transistors. In this paper, it is suggested that the surface of the space charge region of the emitter-base junction is the main source of the base surface 1/f noise. A model is developed which identifies the parameters and describes their interactive contributions to the recombination current at the surface of the space charge region. Based on the theory of carrier number fluctuation and the model of surface recombination current, a 1/f noise model is developed. This model suggests that 1/f noise degradations are the result of the accumulation of oxide-trapped charges and interface states. Combining models of ELDRS, this model can explain the reason why the 1/f noise degradation is more severe at a low dose rate than at a high dose rate. The radiations were performed in a Co~(60) source up to a total dose of 700 Gy(Si). The low dose rate was 0.001 Gy(Si)/s and the high dose rate was 0.1 Gy(Si)/s. The model accords well with the experimental results.