MOCVD生长的未掺杂的In1-xGaxP中的本征缺陷

利用深能级瞬态谱（ Ｄ Ｌ Ｔ Ｓ）和瞬态光电阻率谱（ Ｔ Ｐ Ｒ Ｓ）研究了利用金属有机物化学气相沉淀（ Ｍ Ｏ Ｃ Ｖ Ｄ）方法生长的未有意掺杂的 Ｉｎ１－ ｘ Ｇａｘ Ｐ中缺陷对载流子的俘获和发射过程。利用 Ｄ Ｌ Ｔ Ｓ测量观测到了一个激活能为０３５ ｅ Ｖ 的缺陷,由 Ｔ Ｐ Ｒ Ｓ测量确定该缺陷的俘获势垒值介于１８０ ｍ ｅ Ｖ 到２４０ｍ ｅ Ｖ 之间。该缺陷的俘获势垒值的大的分布解释为缺陷周围原子重组的微观波动。同时在 Ｔ Ｐ Ｒ Ｓ测量中观测到俘获势垒为００６ ｅ Ｖ 和０４０ ｅ Ｖ 的两个缺陷。     

MOCVD生长的未掺杂的In1—xxGaxP中的本征缺陷

利用能级瞬态谱（ＤＬＴＳ）和瞬态光阻率谱（ＴＰＲＳ）研究了利用金属有机物化学气相沉淀（ＭＯＣＶＤ）方法生长的未有间 杂的Ｉｎ１－ｘＧａｘＰ中缺陷对载流子的俘获和发射过程,利用ＤＬＴＳ测量观测到了一个激活能为０．３５ｅＶ的缺陷,由ＴＰＲＳ测量确定该缺陷的俘获势垒值介于１８０ｍｅＶ到２４０ｍｅＶ之间。该缺陷的俘获势垒值的大的分布解释为缺陷周围原子重组的微观波动。同时在ＴＰＲＳ测量中服获获势垒为０．０６     

In0.53Ga0.47As／InP异质结光电二极管的深能级

采用深能级瞬态谱仪（ＤＬＴＳ）测定了Ｉｎ０．５３Ｇａ０．４７Ａｓ／ＩｎＰ异质结光电二极管的ＤＬＴＳ谱。发现存在一电子陷阱，该陷阱能级位于导带底以下０．４４ｅＶ处，能级密度为３．１０×１０１３ｃｍ－３，电子俘获截面为１．７２×１０－１２ｃｍ－２。由于深能级的存在，导致了该器件存在一种新的“暗电流”──“深能级协助隧穿电流”。     

等效深中心研究新方法——瞬态光霍耳和光电阻率谱

考虑到深中心俘获与发射载流子对自由载流子浓度的影响而对中心俘获过程进行了推导与讨论, 了以瞬态光霍耳谱测量和瞬态光电阻率谱测量为基础的两套新的深能级分析测试手段,并证明了其等效性,用此方法测量样品做结,且对大浓度的深中心也可不做任何修正,尤其适用于缺陷对载流子俘获机制的研究,因而弥补了深能级态谱技术的不足。     

InAs自组织生长量子点的空穴俘获势垒

成功地用深能级瞬态谱（ＤＬＩＳ）研究了ｐ 型ＩｎＡｓ 自组织生长的量子点的电学性质,测得２．５ 原子层ＩｎＡｓ 量子点空穴基态能级在ＧａＡｓ 价带底上约０．０９ｅＶ,该量子点在荷电状态发生变化时需要克服一个势垒,俘获势垒高度为０．２６ｅＶ．本工作首次利用ＤＬＴＳ测定了量子点空穴的基态能级和俘获势垒,相信对增加量子点性质的理解会起到有益的帮助     

n-Hg_（1－x）Cd_xTe中复合中心

利用深能级瞬态谱（ＤＬＴＳ）研究了Ｈｇ１－ｘＣｄｘＴｅ（ｘ＝０．４）ｐ＋ｎ结中Ｈ２（０．２９）空穴陷阱的俘获机制，发现它不满足级联复合机制或俄歇复合机制，该能级俘获截面的温度关系满足σ（Ｔ）＝σ∞ｅｘｐ（－ＥＢ／ｋＴ）形式，推测多声子无辐射复合起着决定性作用     

InAs自组织生长量子点的电子俘获势垒

成功地用深能级瞬态谱（ＤＬＴＳ）研究了ＩｎＡｓ自组织生长的量子点电学性质，获得２．５原子层ＩｎＡｓ量子点电子基态能级在ＧａＡｓ导带底下约０．１３ｅＶ，该量子点在荷电状态发生变化时伴随有晶格弛豫，对应俘获势垒为０．３２ｅＶ．本工作也证明可以把量子点类比深中心进行研究．     

GeSi／Si应变结构内应力纵向分布

利用深能级瞬态谱（ＤＬＴＳ）研究分子束外延ｎ－Ｇｅ０．２Ｓｉ０．８／Ｓｉ应变超晶格，观察到两个与位错有关的深中心，其中一个能级位置在ＥＣ＝０．４２ｅＶ，另一个随着偏压变化而发生明显的移动，深能级位置从ＥＣ＝０．２１ｅＶ变化到ＥＣ＝０．２７６ｅＶ，我们认为是内应力引起的．取该深能级的流体静压力系数γ＝６．５９ｍｅＶ／Ｋｂａ，求出超晶格中的应力分布与计算值符合较好．在此基础上提出了一种通过测量深能级随应力移动效应来确定应变结构内应力纵向分布的新方法．     

InAs自组织生长量子点超晶格的电学性质

我们利用深能级瞬态谱（ＤＬＴＳ）研究了一系列ＩｎＡｓ自组织生长的量子点超晶格样品，确认样品中存在体ＧａＡｓ缺陷能级ＥＬ２和ＩｎＡｓ量子点电子基态能级．测得１．７和２．５原子层ＩｎＡｓ量子点电子基态能级相对于ＧａＡｓ的导带底分别为１００ｍｅＶ和２１０ｍｅＶ，量子点电子基态的俘获势垒分别为０．４８ｅＶ和０．３０ｅＶ．     

InGaAs／GaAs应变层量子阱激光器深中心行为

应用深能级瞬态谱（ＤＬＴＳ）技术研究分子束外延（ＭＢＥ）和二次液相外延（ＬＰＥ）生长的ＩｎＧａＡｓ／ＧａＡｓ应变层量子季阱激光器深中心行为．在ＭＢＥ激光器的ｎ－ＡｌｘＧａ１－ｘＡｓ组分缓变层和限制层里，除众所周知的ＤＸ中心外，还观察到有较大俘获截面的深（空穴、电子）陷阱及其相互转化．这些陷阱可能分布在ｘ从０到０．４０和ｘ—０．４０的ｎ－ＡｌｘＧａ１－ｘＡｓ层里ｘ值不连续的界面附近．而在ＬＰＥ激光器的ｎ－ＡｌｘＧａ１－ｘＡｓ组分缓变层和限制层里，ＤＸ中心浓度明显减少，且深（空穴、电子）陷阱消失     

The use of spatially-dependent carrier capture rates for deep-level-defect transient studies

The spatial dependence of the free carrier capture rate for the defect states located near the edge of the depletion layer is investigated. A theoretical treatment is presented here to illustrate the strong variation of the capture rate near the depletion edge with distance. If a transient capacitance technique is used to observe this capture transient, computer-calculated data confirm that the resulting signal comes only from the capture of electrons by those states located near the point at which the Fermi level and the deep level intersect. The capture of electrons by the states that are located in regions other than near the intersection point does not contribute to the detectable signal. Thus the transient signal measures the empty state concentration in a narrow region. Since the electric field in the narrow region can be accurately chosen by the use of different reverse pulse heights, the empty state concentration at the region can be controlled by the emission at different field strengths. The electric field dependence of the emission rate can be measured directly from the capture transient capacitance. Detailed comparisons of the calculated and experimentally measured data show good agreement. Possible applications using this technique in study of deep-level defects are outlined.     

Determination of the electric field at interfaces inamorphous-silicon devices using time-of-flight measurements

The built-in electric field in hydrogenated amorphous silicon (a-Si:H) Mo-Schottky diodes is estimated using voltage transient measurements generated by a sophisticated time-of-flight or time-resolved photoconductivity experiment with a rather high time resolution of 1 ns. The actual determination of the electric field is done by inverse modeling. The simulator (forward model) for the voltage transient is based on the complete set of transport equations for the charge carriers, including surface recombination. The significance of the diffusion and surface recombination is clearly shown by comparing simulated and measured voltage transients     

Field enhanced carrier generation in MOS-capacitors containing defects

Minority carrier generation lifetime was measured as a function of depletion width on wafers with different densities of defects. The results were compared with theoretical predictions for field enhanced carrier emission from coulomb centers. We found that capacitors with a very low lifetime due to stacking faults or metallic precipitations show a drastically enhanced field dependence of generation rate. Agreement with theory can be obtained if we assume a locally enhanced electric field at the defects which can be one order of magnitude higher than the average bulk field.     

光电探测器的电噪声及其应用

电噪声检测方法正在成为一种无损的电子器件可靠性表征手段,而人们对其在光电探测器方面应用的研究还较少.本文在总结光电探测器电噪声类型及产生机理的基础上,分析了光电探测器与电噪声相关的各项性能参数.电噪声不仅是影响光电探测器性能的重要物理量,而且与光电探测器材料缺陷、界面缺陷及深能级陷阱存在相关性.构造的适当噪声参量可以表征光电探测器中的上述缺陷.与电噪声相关的缺陷往往是导致器件失效的因素,借鉴电噪声用于金属-氧化物-半导体场效应晶体管质量和可靠性表征的方法,本文提出了电噪声在表征光电探测器质量和可靠性方面的应用.     

Magnetic field attenuation of nonlinear shields

The analysis of shielding performance of planar shields against near field sources is carried out in the time domain to account for the nonlinear behavior of ferromagnetic materials used in low frequency applications. To this end, the Schelkunoff approach for shielding problems has been reformulated in the time domain introducing the transient wave impedances which relates transient electric and magnetic field components and appear in the integrodifferential boundary conditions. The final equation system is solved by means of a numerical procedure based on the finite element method. The obtained results are compared with analytical and measured data in different configurations     

Detection of traps induced and activated by high field stress in an N-channel VDMOSFET transistor using current deep level transient spectroscopy (CDLTS)

Commercial VDMOSFETs transistors were subjected to positive and negative high field stress. A new model of current deep level transient spectroscopy (CDLTS) characterization is adopted in a research of defects induced and activated by electrical stress. This model is based on pulse width scan instead of classical temperature scan. The band gap is scanned by varying the pulse base level. Positive and negative high field stresses were applied for different periods ranging from 30 to 120 min. After each stress period, activation energies and capture cross sections of detected traps were estimated. Different defects were detected and we have distinguished the doping levels and interface states from deep levels located in the forbidden band gap.     

用深能级瞬态谱法测量GaAS MESFET中的深能级

本文介绍了用深能级瞬态谱(DLTS)法测量GaAs MESFET的深能级杂质和缺陷。在有源层中一般没有测到深能级杂质和缺陷,但在有源层与缓冲层界面附近测到了多个空穴陷阱和电子陷阱。其中空穴陷阱的能级有0.41eV、0.53eV、0.68eV、0.91eV;电子陷阱的能级有0.30eV、0.44eV、0.84eV。并对部分陷阱的性质作了初步的讨论。     

雷电近区电场峰值及其变化率随距离的变化研究

闪电近区电场具有瞬时性和高强度的特点,在雷电防护工程设计及雷电效应测试中,往往需要根据雷电所产生的脉冲辐射强度采取相应的防护、测试措施,在雷电防护标准规范中应明确给出距离雷电通道不同距离处的电场峰值及其变化率的变化情况.文中在传输线（transmission-line,TL）模型的基础上,对雷电近区电场峰值及其变化率随距离的变化进行近似表达,并与相关文献报道的实测数据进行了对比.结果表明,近似表达式的结果与文献报道的实测数据及课题组野外实际观测数据较为吻合,可用于表征距离雷电通道1 km范围内电场峰值和电场变化率的变化,对实际防雷设计和相关的效应测试具有一定的指导意义.     

运动舰船切割地磁场在海水中产生的电场计算

根据经典的Sommerfeld赫兹矢量分别推导出了空气和海水中水平直流电流元的电磁场表达式.在此基础上,根据瞬态连续性原理,推导出了运动舰船切割地磁场磁力线而产生的感应电场.以日本宙斯盾导弹驱逐舰"金刚"号为例,计算了它的感应电场大小及空间分布情况.结果表明,航速20kn时在离船壁5m左右能产生几个毫伏/米的感应电场,在目前的检测技术下该电场是完全可测的,并且该电场在空间分布有明显的特征.     

Implications of gate-edge electric field in AlGaN/GaN high electron mobility transistors during OFF-state degradation

Gate degradation in high electron mobility transistors (HEMTs) under OFF-state stress results from the high electric field near the gate edge. We investigate the evolution of this field over time in AlGaN/GaN HEMTs upon OFF-state stress using a combination of electroluminescence (EL) microscopy and spectroscopy. EL analysis suggests that the electric field at the sites of generated surface defects is lowered after the stress, with greater lowering at higher stress temperature. The ON-state EL spectrum remains unchanged after the stress, suggesting that the regions without generated defects are not affected during the degradation. A finite element model is employed to further demonstrate the effect of surface defects on the local electric field. A correlation is observed for the spatial distribution of the EL intensity before and after the generation of leakage sites, which provides a prescreening method to predict possible early failures on a device.