Radiation damage of Ge-on-Si devices

The radiation damage induced by 2-MeV electrons and 70-MeV protons in p⁺n diodes and p-channel MOS transistors, fabricated in epitaxial Ge-on-Si substrates is reported for the first time. For irradiation above 5×10¹⁵ e/cm², it is noted that both the reverse and forward current increase, and that the forward current is lower after irradiation for a forward voltage larger than about 0.5 V. The reason for this might be an increased resistivity of the Ge-on-Si substrate. For p-MOSFETs, for a 1×10¹⁶ e/cm² dose, a slight negative shift of the threshold voltage and a decrease of the drain current for input and output characteristics have been observed. In addition, g_m decreases after irradiation. The degradation of the transistor performance is thought to be due to irradiation-induced positive charges in the high-κ gate dielectric. The induced lattice defects are also mainly responsible for the leakage current increase of the irradiated diodes.     

Radiation damage effects on bipolar and MOS devices in X-Ray lithography

Radiation damage effects of bipolar and MOS transistors have been investigated using the vacuum ultraviolet (VUV) storage ring of the national synchrotron light source (NSLS). The devices under investigation were exposed to x-ray radiation and electrical measurements were performed to determine the radiation effects on device parameters. It was found for bipolar devices that the current gain is the parameter that is most sensitive to x-ray irradiation. The current gain decreases as the dose increases and the degradation reaches saturation at 1000 mJ/cm². Upon annealing in forming gas at 400° C for 30 min, the current gain recovered its pre-irradiation value and stress test did not show any reliability problem. Bothn-channel andp-channel MOS devices with polysilicon gates were investigated. Host of the relevant device parameters were measured before and after irradiation and after annealing. Upon irradiation the threshold voltage shows the most obvious shift, which was more negative in both cases. However, thep- channel devices experienced a much larger shift than then-channel ones. The transconductance of the devices also experienced a shift.     

Potential of asymmetrical Si/Ge and Ge/Si based hetero-junction transit time devices over homo-junction counterparts for generation of high power

Static and dynamic properties of both complementary n-Ge/p-Si and p-Ge/n-Si hetero-junction Double-Drift IMPATT diodes have been investigated by an advanced and realistic computer simulation technique, developed by the authors, for operation in the Ka-, V- and W-band frequencies. The results are further compared with corresponding Si and Ge homo-junction devices. The study shows high values of device efficiency, such as 23%, 22% and 21.5%, for n-Ge/p-Si IMPATTs at the Ka, V and W bands, respectively. The peak device negative conductances for n-Si/p-Ge and n-Ge/p-Si hetero-junction devices found to be 50.7 ? 10⁶ S/m² and 71.3 ? 10⁶ S/m², which are ～3-4 times better than their Si and Ge counterparts at the V-band. The computed values of RF power-density for n-Ge/p-Si hetero-junction IMPATTs are 1.0 ? 10⁹, 1.1 ? 10⁹ and 1.4 ? 10⁹ W/m², respectively, for Ka-, V- and W-band operation, which can be observed to be the highest when compared with Si, Ge and n-Si/p-Ge devices. Both of the hetero-junctions, especially the n-Ge/p-Si hetero-junction diode, can thus become a superior RF-power generator over a wide range of frequencies. The present study will help the device engineers to choose a suitable material pair for the development of high-power MM-wave IMPATT for applications in the civil and defense-related arena.     

Potential of asymmetrical Si/Ge and Ge/Si based hetero-junction transit time devices over homo-junction counterparts for generation of high power

Static and dynamic properties of both complementary n-Ge/p-Si and p-Ge/n-Si hetero-junction Double-Drift IMPATT diodes have been investigated by an advanced and realistic computer simulation technique,developed by the authors,for operation in the Ka-,V- and W-band frequencies.The results are further compared with corresponding Si and Ge homo-junction devices.The study shows high values of device efficiency,such as 23%, 22%and 21.5%,for n-Ge/p-Si IMPATTs at the Ka,V and W bands,respectively.The peak device negative conductances for n-Si/p-Ge and n-Ge/p-Si hetero-junction devices found to be 50.7×10~6 S/m~2 and 71.3×10~6 S/m~2, which are～3-4 times better than their Si and Ge counterparts at the V-band.The computed values of RF power-density for n-Ge/p-Si hetero-junction IMPATTs are 1.0×10~9,1.1×10~9 and 1.4×10~9 W/m~2,respectively,for Ka-,V- and W-band operation,which can be observed to be the highest when compared with Si,Ge and n-Si/p-Ge devices.Both of the hetero-junctions,especially the n-Ge/p-Si hetero-junction diode,can thus become a superior RF-power generator over a wide range of frequencies.The present study will help the device engineers to choose a suitable material pair for the development of high-power MM-wave IMPATT for applications in the civil and defense-related arena.     

GaInP/GaAs/Ge三结太阳电池辐照损伤效应及加固技术研究进展

文章首先重点介绍了国内外开展GaInP/GaAs/Ge三结太阳电池的电子、质子及其他辐射粒子或射线辐照实验的研究进展,然后从辐照损伤效应的仿真模拟研究、抗辐射加固技术、损伤预估方法等方面综述了GaInP/GaAs/Ge三结太阳电池辐照损伤效应及加固技术的研究进展,最后梳理了当前GaInP/GaAs/Ge三结太阳电池辐照损伤效应研究中亟待解决的关键技术问题,为深入开展GaInP/GaAs/Ge三结太阳电池辐照损伤效应实验方法标准制定、损伤机理分析、在轨寿命预估及抗辐射加固技术研究提供了理论指导和实验技术支持。     

X-ray lithography induced radiation damage in CMOS and bipolar devices

Radiation effects from a synchroton x-ray lithography source on the performance degradation and long term reliability of high performance self-aligned bipolar devices and deep sub-micron CMOS devices are studied. The hot-carrier properties of the x-ray induced damage in CMOS devices, such as interface states, positive oxide charges and neutral traps have been examined. The effect of these radiation induced defects and their impact on the DRAM circuits in terms of the performance and reliability are discussed. In the self-aligned, double polysilicon bipolar transistor structure interface states and trapped charges can be generated by the radiation source in the sidewall oxide near the emitter-base junction such damage can increase the emitter-base leakage current. This increase of base current can substantially degrade the device current gain at low bias.     

高能粒子辐射掺锗直拉硅中锗对空位,间隙原子运动的影响

高能粒子辐射掺锗直拉硅中锗可以在硅的晶格结构中产生膨胀场,其引起的附加势能使邻近的空位、间隙原子的周期性的运动势场发生变化,从而锗作为湮灭中心,增大了空位与间隙原子的复合率。     

离子束溅射技术制备Ge—SiO2纳米颗粒镶嵌薄膜的微结构和光学性质研究

采用透射电子显微镜（ＴＥＭ）对Ｇｅ－ＳｉＯ２纳米颗粒镶嵌薄膜样品的形和结构进行了观察研究。测量了不同直径纳米锗颗粒镶嵌薄吸收光谱，并砂同激光光能量下对样品进行了室温荧光光谱研究，发现在中心波长为４２０ｎｍ处有一个较强的光致荧光峰。研究结果表明纳米锗粒子的相结构和电子能级结构同常规的大块锗晶体相比均发生显著的改变。     

YON界面钝化层改善HfO2/Ge界面特性的研究

本文采用YON界面钝化层来改善HfO₂栅介质Ge metal-oxide-semiconductor（MOS）器件的界面质量和电特性.比较研究了两种不同的YON制备方法：在Ar+N₂氛围中溅射Y₂O₃靶直接淀积获得以及先在Ar+N₂氛围中溅射Y靶淀积YN再于含氧氛围中退火形成YON.实验结果及XPS的分析表明,后者可以利用YN在退火过程中先于Ge表面吸收从界面扩散的O而氧化,从而阻挡了O扩散到达Ge表面,更有效抑制了界面处Ge氧化物的形成,获得了更优良的界面特性和电特性：较小的CET（1.66 nm）,较大的k值（18.8）,较低的界面态密度（7.79×10¹¹ eV^-1cm^-2）和等效氧化物电荷密度（-4.83×10¹² cm^-2）,低的栅极漏电流（3.40×10^-4 A/cm²@V_g=V_fb+1 V）以及好的高场应力可靠性.     

GaAs/Ge heterojunction grown by metal-organic chemical vapor deposition and its application to high efficiency photovoltaic devices

We have studied the heteroepitaxial growth of GaAs on Ge substrates by metal-organic chemical vapor deposition (MOCVD). Different growth conditions and substrate orientations were employed to examine the properties of GaAs grown upon Ge substrates, and in particular the GaAs/Ge interface. The interface properties were found to strongly depend on growth conditions. By small changes in the growth temperature, the GaAs/ Ge interface was altered from active to passive. Only a narrow temperature window (600 to 630° C) for the initial GaAs layer growth gave the passive-Ge junction together with good surface morphology. Accordingly, a high efficiency (19%, AMO) GaAs solar cell was grown by atmospheric pressure MOCVD on a Ge substrate without any junction in the Ge.     

超薄HfN界面层对HfO2栅介质Ge pMOSFET电性能的改进

通过在高k介质和Ge表面引入一层超薄HfN界面层,实验制备了HfO2/HfON叠层栅介质Ge MOS器件。与没有界面层的样品相比,HfO2/HfON叠层栅介质MOSFET表现出低的界面态密度、低的栅极漏电和高有效迁移率。因此利用HfON作为Ge MOS器件的界面钝化层对于获得小的等效氧化物厚度和高的high-k/Ge界面质量有着重要的意义。     

近红外Si_(0.8)Ge_(0.2)/Si横向pin探测器的模拟与测试

设计了一种新型叉指状近红外 Si0 .8Ge0 .2 / Si pin横向光电探测器。采用半导体器件模拟软件 Atlas分别对该器件平衡条件下物理特性及反向偏压下电场分布、光电特性进行了模拟 ;对实际制作的光电探测器进行了测试 ,结果表明 :其波长响应范围为 0 .4～ 1 .3μm,峰值响应波长在 0 .93μm,响应度达 0 .3 8A/ W,寄生电容小于 2 .0 p F。实验结果和模拟结果符合得很好。其良好的光电性能为应用于近红外光的高速、低工作电压硅基光电集成器件提供了可能     

MOS器件及电路的总剂量辐射效应测试技术

介绍了半导体器件与电路的总剂量辐射效应及其测试技术,主要分析了MOS器件的效应机理、总剂量效应试验模拟源以及各种模拟源辐射环境的测量方法,最后给出了部分实验结果,并对其进行了讨论。     

Mechanical and electronic properties of Si,Ge and their alloys in P42/mnm structure

Structural, mechanical, and electronic properties of Si–Ge alloys in P4₂/mnm structure were studied using first-principles calculations by Cambridge Serial Total Energy Package (CASTEP) plane-wave code. The calculations were performed with the local density approximation and generalized gradient approximation in the form of Perdew–Burke–Ernzerhof, PBEsol. The calculated excess mixing enthalpy is positive over the entire germanium composition range. The calculated formation enthalpy shows that the Si–Ge alloys are unstable at 0 K; however, the alloys might exist at specified high temperature scale. The anisotropic calculations show that Si₁₂ in P4₂/mnm structure exhibits the greatest anisotropy in Poisson’s ratio, shear modulus, Young’s modulus and the universal elastic anisotropy index A^U, but Si₈Ge₄ has the smallest anisotropy. The electronic structure calculations reveal that Si₁₂ and Si–Ge alloys in P4₂/mnm structure are indirect band gap semiconductors, but Ge₁₂ in P4₂/mnm structure is a direct semiconductor.     

Ge/Si(100)界面互扩散的喇曼光谱

利用喇曼光谱研究了不同温度下在Si(100)衬底上异质外延Ge层由于扩散引起的Ge/Si异质结界面互混以及表面活化剂Sb对其的影响.结果表明表面活化剂Sb的存在大大抑制了界面的互扩散,在650℃下也没有观察到明显的界面互混.没有Sb时,在500℃下已存在一定程度的界面互混,界面互混程度随外延层生长温度的增高而增强.这种互扩散的差别与成岛生长时应变释放有关     

In2Ge2O7薄膜制备及其紫外光敏特性研究

以In2O3和GeO2为原料,采用碳还原法制备了In2Ge2O7多晶薄膜,利用XRD和SEM对薄膜的结构和形貌进行了表征。对基于In2Ge2O7薄膜的金属-半导体-金属(MSM)紫外探测器进行了紫外光电导特性测量,结果显示:在波长为250nm的紫外光照射下,在5V偏压下,器件的光电流为727μA(暗电流为12μA),光响应度达到262.9A.W-1,光响应上升时间约为67s,下降时间约为15s。分析认为较长的响应时间是由于内部的缺陷与位错造成的。初步研究结果表明:In2Ge2O7薄膜可以作为一种良好的日盲紫外探测材料。     

Ge2Sb2Te5的电化学特性及化学机械抛光

从电化学角度研究了Ge2Sb2Te5薄膜在化学机械抛光液中的作用，以及不同的pH值和H2O2浓度下的电化学特性. 采用Solartron SI1287电化学设备测试了Ge2Sb2Te5薄膜在溶液中的开路电位和动电位扫描. 开路电位结果表明：Ge2Sb2Te5在pH值为10的抛光液中表现出钝化行为；而抛光液的pH值为11时，开始向活化转变；当pH值为12时，薄膜处于活化状态. 在动电位扫描过程中，不同的pH值和H2O2浓度下，薄膜的扫描曲线形状相似，表明薄膜腐蚀具有相同的反应机理. 自制碱性抛光液，对Ge2Sb2Te5薄膜进行化学机械抛光，用SEM和EDS对抛光后的结构进行分析. 结果表明，通过CMP实现了Ge2Sb2Te5填充结构.     

硅离子注入对Ge2Sb2Te5结构和电阻的影响

采用磁控射频溅射法制备了Ge2Sb2Te5薄膜，利用离子注入法研究了硅掺杂对薄膜结构和电阻性能的影响. 研究发现，由于硅的掺杂，Ge2Sb2Te5薄膜的结构不仅保留了原有的面心立方低温晶相和六方高温晶相，而且出现了菱形六面体的Sb2Te3晶相；掺杂硅后，Ge2Sb2Te5薄膜的电阻有较大变化，晶态电阻的提高有利于降低非晶化相变过程的操作电流，薄膜电阻-温度稳定性的改善可保证有较宽的操作电流波动范围.     

ZrON/GeON 双钝化层改善Ge MOS器件的界面特性和电特性

本文研究了利用等离子体氮化形成ZrON/GeON双钝化层制备Ge MOS器件的界面特性和电特性。结果发现,相比于N2等离子处理,NH3等离子处理制备的双钝化层显著改善了器件的界面和电特性,获得了低的界面态密度 (Dit = 1.64×1011 cm-2 eV-1)和栅极漏电流(Jg = 9.32×10-5 A cm-2@Vfb +1 V),小的电容等效厚度 (CET = 1.11 nm)以及高的k值 (32). XPS分析表明,由NH3等离子体分解出的H原子和NH基团可以有效促进Ge表面不稳定低k GeOx的挥发,从而形成了高质量的GeON钝化层;且NH3等离子体氮化导致更多氮在ZrON/GeON中结合,能更有效阻止O、Ti、Ge等元素间的相互扩散,从而获得好的界面质量和电特性。     

Ge,Al共掺SiO2薄膜的发光性能研究

用射频磁控溅射法制备Ge,Al共掺SiO2复合薄膜并以不同温度进行退火,得到具有特定光致发光性质的复合材料。经600℃退火的薄膜样品在260 nm谱线激发下,主要有398和494 nm发光峰。通过对样品的X射线衍射谱和X射线光电子能谱的测试,确定了薄膜的结构特征,同时对观察到的光致发光从理论上做了重点分析,认为双重配位的Si孤对中心和GeO色心中的三重激发态到基态(T1→S0)之间的辐射跃迁分别是产生414和398 nm发光峰的主要原因。实验结果表明,Al的掺入可能在GeO2晶粒中引入了新缺陷能级,从而产生494 nm这一特殊的发光带,同时Al的掺入也提高了398 nm发光峰的发光效率。