应变Si1－xGex/(111)Si空穴有效质量模型

利用应变Si_1-xGe_x/(111)Si材料价带E(k)-k关系,研究获得了沿不同晶向的空穴有效质量,并在此基础上,建立了空穴各向同性有效质量模型.结果表明,与弛豫材料相比,应变Si_1-xGe_x/(111)Si材料价带带边空穴有效质量各向异性更加显著,带边空穴各向同性有效质量随Ge组分明显减小.该研究成果可为Si基应变PM 关键词： 1-xGe_x')" href="#">应变Si_1-xGe_x 空穴有效质量 价带     

应变Si/(001)Si1-xGex空穴有效质量各向异性

基于应变Si/（001）Si_1-xGe_x材料价带E（k）-k关系模型,研究获得了其沿不同晶向的空穴有效质量.结果表明,与弛豫材料相比,应变Si/（001）Si_1-xGe_x材料价带带边（重空穴带）、亚带边（轻空穴带）空穴有效质量在某些k矢方向变化显著,各向异性更加明显.价带空穴有效质量与迁移率密切相关,该研究成 关键词： 应变Si 价带 空穴有效质量     

应变Si/(001)Si1-xGex电子迁移率

依据离化杂质散射、声学声子散射和谷间散射的散射模型,在考虑电子谷间占有率的基础上,通过求解玻尔兹曼方程计算了不同锗组分下,不同杂质浓度时应变Si/(001)Si_1-xGe_x的电子迁移率.结果表明:当锗组分达到0.2时,电子几乎全部占据Δ₂能谷;低掺杂时,锗组分为0.4的应变Si电子迁移率与体硅相比增加约64%;对于张应变Si NMOS器件,从电子迁移率角度来考虑不适合做垂直沟道.选择相应的参数,该方 关键词： 电子谷间占有率 散射模型 锗组分 电子迁移率     

应变Si1-xGex能带结构研究

采用结合形变势理论的K.P微扰法建立了（001）,（101）和（111）面弛豫Si衬底上生长的应变Si_1-xGe_x（x≤0.5）的能带结构模型,获得了其导带带边能级、价带带边能级、导带劈裂能、价带劈裂能及禁带宽度随Ge组分（x）的函数变化关系,该量化数据对器件研究设计可提供有价值的参考． 关键词： 1-xGe_x')" href="#">应变Si_1-xGe_x K.P 法 能带结构     

应变Si/Si1-xGex n型金属氧化物半导体场效应晶体管反型层中的电子迁移率模型

为了描述生长在弛豫Si_1-xGe_x层上应变Si n型金属氧化物半导体场效应晶体管(nMOSFETs)反型层中电子迁移率的增强机理,提出了一种新型的、基于物理的电子迁移率模型.该模型不仅能够反映声学声子散射迁移率、表面粗糙度散射迁移率与垂直于半导体-绝缘体界面的电场强度之间的依赖关系,而且也能解释不同的锗组分对两种散射机理的抑制情况从而引起电子迁移率增强的机理.该模型数学表达式简单,可以模拟任意锗组分下的迁移率.通过数值分析验证得出,该 关键词： 应变Si/SiGe 电子迁移率 反型层 模型     

Si1-xGex合金半导体中CiCs和CiOi缺陷随Ge含量的变化

采用从头计算(ab initio)的方法对Si和Si_1-xGe_x合金半导体材料中C_iC_s缺陷的性质进行探讨,同时也对比调查了C_iO_i缺陷在Si和Si_1-xGe_x合金中的性质. 在不同Ge含量的Si_1-xGe_{x关键词： 1-x}Ge_x合金')" href="#">Si_1-xGe_x合金 从头计算法 iC_s缺陷')" href="#">C_iC_s缺陷 iO_i缺陷')" href="#">C_iO_i缺陷     

应变Si/(001)S1－xGex本征载流子浓度模型

利用应变Si CMOS技术提高载流子迁移率是当前研究发展的重点,本征载流子浓度是应变Si材料的重要物理参数,也是决定应变Si器件电学特性的重要参量.本文基于K.P理论框架,从分析应变Si/（001）Si_1-xGe_x材料能带结构出发,详细推导建立了300K时与Ge组分（x）相关的本征载流子浓度模型.该数据量化模型可为Si基应变器件物理的理解及器件的研究设计提供有价值的参考. 关键词： 应变Si 有效态密度 本征载流子浓度     

利用Keating模型计算Si（1-x）Gex及非晶硅的拉曼频移

利用Keating模型计算了Si_（1-x）Ge_x合金中Si—Si,Ge—Ge和Si—Ge三种振动模态的拉曼频移,计算分别获得Ge浓度为01,05和09时,Si—Ge的振动拉曼频移分别为40275,41339和38815 cm^-1,这些结果与文献的实验结果符合,证明了Keating模型建立的关于原子振动模型是有效的,并可以利用拉伸压缩和相邻原子键之间弹性系数变化获得处于应变状态的拉曼光谱频率.利用Kea 关键词： Keating模型 拉曼光谱 （1-x）Ge_x')" href="#">Si_（1-x）Ge_x 非晶硅     

第一性原理研究应变Si/(111)Si1-xGex能带结构

基于密度泛函理论框架的第一性原理平面波赝势方法对双轴应变Si/(111) Si_1-xGe_x(x=0.1—0.4)的能带结构进行了研究,结果表明：导带带边六度简并没有消除;应变部分消除了价带带边的简并度;导带带边能量极值k矢位置和极值附近可由电子有效质量描述的能带形状在应变条件下几乎不变;价带极大值附近可由空穴有效质量描述的能带形状随着x有规律地变化. 此外,给出的禁带宽度与x的拟 关键词： 应变硅 能带结构 第一性原理     

Phonon Limited Electron Mobility in Germanium FinFETs:Fin Direction Dependence

We investigate the phonon limited electron mobility in germanium(Ge) fin field-effect transistors(FinFETs)with fin rotating within(001),(110),and(111)-oriented wafers. The coupled Schrodinger-Poisson equations are solved self-consistently to calculate the electronic structures for the two-dimensional electron gas, and Fermi's golden rule is used to calculate the phonon scattering rate. It is concluded that the intra-valley acoustic phonon scattering is the dominant mechanism limiting the electron mobility in Ge FinFETs. The phonon limited electron motilities are influenced by wafer orientation, channel direction, in thickness Wfin, and inversion charge density Ninv. With the fixed Wfin, fin directions of(110),(112) and(110) within(001),(110), and(111)-oriented wafers provide the maximum values of electron mobility. The optimized for mobility is also dependent on wafer orientation and channel direction. As Ninv, increases, phonon limited mobility degrades, which is attributed to electron repopulation from a higher mobility valley to a lower mobility valley as Ninv increases.     

Pressure effect on the electron mobility in AlAs/GaAs quantum wells

By taking the influence of optical phonon modes into account, this paper adopts the dielectric continuum phonon model and force balance equation to investigate the electronic mobility parallel to the interfaces for AlAs/GaAs semiconductor quantum wells (QWs) under hydrostatic pressure. The scattering from confined phonon modes, interface phonon modes and half-space phonon modes are analysed and the dominant scattering mechanisms in wide and narrow QWs are presented. The temperature dependence of the electronic mobility is also studied in the temperature range of optical phonon scattering being available. It is shown that the electronic mobility reduces obviously as pressure increases from 0 to 4GPa, the confined longitudinal optical (LO) phonon modes play an important role in wide QWs, whereas the interface optical phonon modes are dominant in narrow QWs, the half-space LO phonon modes hardly influence the electronic mobility expect for very narrow QWs.     

Determination of the LO phonon energy by using electronic and optical methods in AlGaN/GaN

The longitudinal optical (LO) phonon energy in AlGaN/GaN heterostructures is determined from temperature-dependent Hall effect measurements and also from Infrared (IR) spectroscopy and Raman spectroscopy. The Hall effect measurements on AlGaN/GaN heterostructures grown by MOCVD have been carried out as a function of temperature in the range 1.8-275 K at a fixed magnetic field. The IR and Raman spectroscopy measurements have been carried out at room temperature. The experimental data for the temperature dependence of the Hall mobility were compared with the calculated electron mobility. In the calculations of electron mobility, polar optical phonon scattering, ionized impurity scattering, background impurity scattering, interface roughness, piezoelectric scattering, acoustic phonon scattering and dislocation scattering were taken into account at all temperatures. The result is that at low temperatures interface roughness scattering is the dominant scattering mechanism and at high temperatures polar optical phonon scattering is dominant.     

Raman phonon anomalies in Sr(Fe1-xCox)2As2

Phonon anomalies have been reported in iron-pnictide superconductors indicating a diverse interplay between different orders in the materials.Here,we report Raman scattering measurements on Sr(Fe_1-xCo_x)₂As₂(x=0 and x=0.04)single crystals in the B;symmetry with respect to a 1 Fe unit cell.Upon cooling,we observe a larger split(13 cm;)of Eg Raman phonon modes pertaining to in-plane Fe and As displacements as the crystals undergo the tetragonal-toorthorhombic structural phase transition,although a considerable split(9 cm;)has been reported in BaFe_1-xCo_x)₂As₂.Furthermore,the splitting of E;phonon modes is strongly reduced upon doping.We perform an order-parameter analysis revealing a similar doping dependence of E;phonon splitting as reported in other compounds of the 122 family,indicating these phonon anomalies widely exist in 122 iron-based superconductors and might share the same mechanisms.     

Ge掺杂对InI导电性能影响的第一性原理研究

采用密度泛函理论框架下的第一性原理平面波超软赝势方法,在相同环境条件下对不同浓度Ge掺杂的In I导电性能进行了研究.建立了由不同浓度的Ge原子替代In原子的In1-x Ge x I(x=0,0.125,0.25)模型.对低温下高掺杂Ge原子的In1-x Ge x I半导体的优化参数、总态密度、能带结构进行了计算.结果表明:Ge的掺入使In1-x Ge x I材料的体积减小,总能量升高,稳定性降低;Ge原子浓度越大,进入导带的相对电子数量越多,In1-x Ge x I电子迁移率减小,电阻率增大,同时最小光学带隙也增大,有利于改善体系的核探测性能.     

Investigation of strain effect on the hole mobility in GOI tri-gate pFETs including quantum confinement

The strain impact on hole mobility in the GOI tri-gate pFETs is investigated by simulating the strained Ge with quantum confinement from band structure to electro-static distribution as well as the effective mobility. Lattice mismatch strain induced by HfO2 warps and reshapes the valence subbands, and reduces the hole effective masses. The maximum value of hole density is observed near the top comers of the channel. The hole density is decreased by the lattice mismatch strain. The phonon scattering rate is degraded by strain, which results in higher hole mobility.     

Electron mobility variance in the presence of an electric field: Electron–phonon field-induced tunnel scattering

The problem of electron mobility variance is discussed. It is established that in equilibrium semiconductors the mobility variance is infinite. It is revealed that the cause of the mobility variance infinity is the threshold of phonon emission. The electron–phonon interaction theory in the presence of an electric field is developed. A new mechanism of electron scattering, called electron–phonon field-induced tunnel (FIT) scattering, is observed. The effect of the electron–phonon FIT scattering is explained in terms of penetration of the electron wave function into the semiconductor band gap in the presence of an electric field. New and more general expressions for the electron–non-polar optical phonon scattering probability and relaxation time are obtained. The results show that FIT transitions have principle meaning for the mobility fluctuation theory: mobility variance becomes finite.     

Effects of non-equilibrium polar optic phonons and the band non-parabolicity on small signal high-frequency hot electrons ac mobility in narrow gap semiconductors in high magnetic fields

The small signal high-frequency ac mobility of hot electrons in n-HgCdTe in the extreme quantum limit at low and high temperatures have been calculated considering the non-equilibrium phonon distribution as well as the thermal phonon distribution .The energy loss rate has been calculated considering only optical phonon scattering while the momentum loss rate has been calculated considering acoustic phonon scattering and piezoelectric scattering together with polar optical phonon scattering and separately considering only the polar optical scattering. The results have been discussed and compared. It has been observed that at 20 K, the normalized mobility considering all the three scattering mechanisms differs appreciably from that considering only the polar optical phonon scattering. However, at 77 K, there is no difference in the normalized mobility. This establishes the fact that at higher temperature, the effect of acoustic phonon scattering and piezoelectric coupling is negligible, compared to the polar optical phonon scattering. So the ac mobility considering only polar optical phonon scattering has been studied at 77 and 20 K. The ac mobility is found to remain constant up to 100 GHz and thereafter it started decreasing at higher frequencies at 77 K whereas the ac mobility reduces at much lower frequencies at lower temperature at lower field. The non-parabolicity of the band structure enhances the normalized mobility.     

双能谷效应对N型掺杂Si基Ge材料载流子晶格散射的影响

性能优越的Si基高效发光材料与器件的制备一直是Si基光电集成电路中最具挑战性的课题之一.Si基Ge材料不仅与成熟的硅工艺相兼容,而且具有准直接带特性,被认为是实现Si基激光器最有希望的材料.对Si基Ge材料N型掺杂的研究有利于提示出其直接带发光增强机理.本文研究了N型掺杂Si基Ge材料导带电子的晶格散射过程.N型掺杂Si基Ge材料具有独特的双能谷(Γ能谷与L能谷)结构,它将通过以下两方面的竞争关系提高直接带导带底电子的占有率:一方面,处于Γ能谷的导带电子通过谷间光学声子的散射方式散射到L能谷;另一方面,处于L能谷的导带电子通过谷内光学声子散射以及二次谷间光学声子散射或者直接通过谷间光学声子散射的方式跃迁到Γ能谷.当掺杂浓度界于10~(17)cm~(-3)到10~(19)cm~(-3)时,适当提高N型掺杂浓度有利于提高直接带Γ能谷导带底电子占有率,进而提高Si基Ge材料直接带发光效率.