瞬态C-V法测量AlGaAs:Si中DX中心的电离能(英文)

The thermal ionization energy ET of DX centers in AlxGa1-xAs and its dependence with the value of x and the pressure are very important for estab- lishing the model of DX centers. The conventional DLTS and Hall methods used to DX center measurement have some ambiguities in theoretical analysis and experiments and the values of ET determined are different with those methods. The new constant temperature transient C-V measurement is based on the fact that at low temperature both electron capture and emission rates of DX centers are very slow. During the transient C-V measurement, change; of bias voltages and capacitance measurements are completed in a time duration much shorter than the electron capture and emission time constants, therefore the electrons occupied on the DX centers are considered to be frozen. The density of DX centers, the distribution profile of electrons on DX centers in the depletion region of a Schottky diode at a constant reverse bias, and the density of free electrons in conduction band in the bulk and their temperature dependence have been measured.     

AlGaAs:Si中与DX中心有关的光生电子陷阱特性研究(英文)

A new electron trap state SD was found by DLTS measurement under light illumination in Si doped A.lxGa1-xAs. This new trap energy level ESD is shallower than the DX center energy in the gap and the concentration of SD is comparable to that of DX centers. The emission activation energy Ec=0.20±0.05eV and capture activation energy Ec= 0.17±0.05eV. The SD DLTS peak has never been detected previously because under dark and thermal equilibrium condition most of the electrons occupy the deeper DX states and most of SD states are empty. However, when the sample is illuminated by light, electrons are excited to the conduction band and then re-captured by SD since the deeper DX states have a slower electron capture rate, thus a new DLTS peak corresponding to SD appears. Constant temperature capacitance transient C-t and transient C-V measurements were also used to further confirm the existence of SD states.     

Ⅲ-Ⅴ族半导体准粒子能量的第一性原理赝势计算(英文)

The self-consistent pseudopotential calculation method is used in ab initio calculations of quasiparticle energies for semiconductors with particular attentions paid to GaAs. Although having highly accurate for ground state properties the traditional Density Functional Theory for calculations of many electron systems is not very reliable when applied to excited states. The long standing proble mof underestimations of ab initio calculated energy band gaps for semiconductors and insulators is well known. For Si, Ge and GaAs, e.g., the first principle pssudopotential calculations yield band gaps of 0.52eV, 0.07eV and 0.461eV, respectively, as compared with the experimental measurements of 1.17eV, 0.744eV and 1.51eV. When taking quasiparticle self-energies into account, the excitations (quasiparticle energies) of the many electron systems can be accurately described. The lowest calculated excitation energies above tin highest occupied levels are accurate to within a few percent of experimental band gaps. We have performed ab initio quasiparticle energy calculations for GaAs; our calculated energy band gap Eg= 1.524eV is in excellent agreement with experiments. In Green's function approach GW approximation is utilized, and Generalized Plasma Pole model is used to obtain dynamical dielectric matrix.     

Diagram representations of charge pumping processes in CMOS transistors

A diagram representation method is proposed to interpret the complicated charge pumping(CP) processes. The fast and slow traps in CP measurement are defined.Some phenomena such as CP pulse rise/fall time dependence, frequency dependence,the voltage dependence for the fast and slow traps,and the geometric CP component are clearly illustrated at a glance by the diagram representation.For the slow trap CP measurement,there is a transition stage and a steady stage due to the asymmetry of the electron and hol...     

瞬态C-V方法对Al_xGa_(1-x)As中DX中心的研究

本文指出DX中心电容测量中边区的重要性,提出一种新的瞬态C-V方法,可以用来测量DX中心浓度、导带电子浓度和边区的空间电荷分布及导带电子浓度随温度的变化关系,并由此导出测量DX中心热电离能的方法。另外,还对DX中心正∪和负∪两种模型的理论分析和实验结果进行了比较,得出不同模型所应满足的附加条件。     

CMOS器件中电荷泵过程的图解表示

我们提出了一种以图解的方式来理解复杂的电荷泵浦 ( CP ) 测量过程的方法。这里我们定义了电荷泵浦测量中的快速和慢速两种缺陷陷阱,并用图解的方式清晰直观地解释了电荷泵浦测量中出现的脉冲上升下降时间相关现象、频率相关现象、快速和慢速成分与测量电压相关现象以及几何效应对电荷泵浦测量的影响。由于电子和空穴的捕获截面不对称,并且测量到的电荷泵浦电流 ( Icp ) 是由捕获截面较小的电子或者空穴成分决定,所以慢速陷阱的电荷泵测量中含有动态和稳态两个过程。我们还用这个图解的方法讨论了最新发展的改良电荷泵浦 ( MPC ) 方法的合理性。     

深亚微米MOS器件中栅介质层的直接隧穿电流

在WKB近似的理论框架下,提出了一个MOS器件中栅介质层直接隧穿电流的模型.在这个模型中,空穴量子化采用了一种改进的单带有效质量近似方法,这种方法考虑了价带的混合效应.通过与试验结果的对比,证明了这个模型可以适用于CMOS器件中电子和空穴的隧穿电流.还研究了介质层能隙中的色散对隧穿电流的影响.这个模型还可以进一步延伸到对未来高介电常数栅介质层中隧穿电流的研究.     

B~+和P~+离子注入在n-Si中产生缺陷能级的进一步研究

用快速的电流DLTS和最低温度达10K的低温样品架对过去报道过的n型Si中B~+,200keV,2.5 × 10~(11)cm~(-2)和P~+,240keV,4.4 × 10~(11)cm~(-2)离子注入产生的新能级重新作了测量.在注B~+样品中,发现三个新的电子陷阱E_6(0.16),E_7(0.15),E_8(0.08),其中E_7具有很大的浓度.在注P~+样品中,发现二个新的电子陷阱,其中E_7与注硼样品属于同一种中心,因此可能与硼无关.另一个E_3＂(0.09).     

关于AlGaAs:Si中DX中心的新观点

本文给出DX中心为负U中心时所满足的统计规律。指出它与大量AlGaAs:Si的Hall实验不定量符合。为此我们提出,Si可能形成二种不同的施主NU和SD。NU是产生DX能级的负U中心。SD只形成浅施主能级或电激活中心。两种中心的浓度N~(NU)和N~(SD)可以比拟。且N~(SD)/N~(NU)随Si浓度增加而增加。SD中心作为一种电子源,向NU输送电子,放宽了费米能级钉扎于DX能级的条件,从而与Hall实验相符。并用此观点重新解释了过去的种种实验。     

B~+、P~+离子注入p-Si中产生的缺陷及其退火特性的DLTS研究

本文利用沟道背散射分析技术、剖面透射电子显微镜(XTEM)等对150keV As~+沿〈100〉沟道方向注入硅的基本特征和临界条件进行了分析测试.剂量达到1×10~(14)/cm~2时,浅注入区(0-0.2μm)晶格损伤严重,导致沟道注入效应基本消失.沟道深注入区(0.2-0.6μm)形成均匀的轻度损伤.常规退火后,沟道深注入区内的载流子浓度一般不超过2×10~(17)/cm~3,本文称之为沟道注入饱和浓度.还发现沟道注入造成的非晶层比相同剂量下随机注入造成的非晶层略厚一些.退火后残留的二次缺陷仍在原重损伤层与衬底之间的过渡区.