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1.
A semi analytical model describing the bulk mobility for electrons in strained-Si layers as a function of applied uniaxial strain applied at the gate has been developed in this paper. The uniaxial stress has been applied through the silicon nitride cap layer. The effects of uniaxial stress are understood on all the three components of mobility i.e. phonon, columbic and surface roughness mobility. The results show that the electron mobility is a strong rising function of applied uniaxial strain. Flatband voltage, Depletion Charge density, Inversion charge density, Energy gap and Effective surface electrical field have been analytically modeled. There is a sharp increase in the vertical electrical field and inversion charge density and decrease in the energy gap, depletion charge density and the flatband voltage when the uniaxial stress is applied. The electron mobility results have also been compared with the experimentally reported results and show good agreement.  相似文献   

2.
A low dimensional tight-binding (TB) based bandstructure calculation program is developed for double-gate MOSFETs (DG-FETs) to model the effects of channel orientation, transverse electric field, stress, and geometry-induced quantum confinement. Electron mobility in the strained channel is then evaluated using the Monte Carlo (MC) method, based on the calculated bandstructure. It is concluded that electron mobility is enhanced by the splitting of conduction band valleys and the change of electron effective mass, as a function of layer thickness, crystal orientation and stress in strained Si DG-FETs.  相似文献   

3.
We review modeling techniques used to compute strain induced performance enhancement of modern MOSFETs. While p-channel MOSFETs were intensively studied, electron transport in strained structures received surprisingly little attention. A rigorous analysis of the subband structure in thin silicon films under stress is performed. Calculated subband effective masses are shown to strongly depend on shear strain and film thickness. A decrease of the transport effective mass under tensile stress in [110] direction and an additional splitting between the unprimed subbands with the same quantum number guarantees a mobility enhancement even in ultra-thin (001) silicon films. This increase of mobility and drive current combined with the improved channel control makes multi-gate MOSFETs based on thin films or silicon fins preeminent candidates for the 22 nm technology node and beyond.  相似文献   

4.
A comprehensive study of velocity overshoot and the dependences that might be established with technological parameters in symmetrical DGSOI transistors has been carried out. A one-electron Monte Carlo simulator was used to perform this work. It has been proved that velocity overshoot is dominated by the average conduction effective mass. Thus, when the silicon thickness decreases below 5 nm velocity overshoot peak increases showing the opposite behavior to electron mobility.  相似文献   

5.
Electron transport in strained double gate silicon on insulator transistors has been studied by Monte Carlo method. Poisson and Schroedinger equations have been self-consistently solved in these devices for different silicon layer thicknesses both for unstrained and strained silicon channels. The results show that the strain of the silicon layer leads to a larger population of the no-primed subbands, thus decreasing the average conduction effective mass. However, strain also contributes to a larger confinement of the charge close to the two Si/SiO2 interfaces, thus weakening the volume inversion effect, and limiting the potential increase of the phonon limited mobility.  相似文献   

6.
库水位反复升降过程中堆石体的应力状态表现为偏应力基本恒定、球应力往复循环变化,为探求球应力循环条件下堆石料的变形规律,以取自现场的堆石材料为研究对象,通过控制孔隙水压力来实现球应力增大–减小的低速循环应力路径静力三轴试验。研究结果表明:偏应力恒定、球应力循环条件下,体应变随球应力的减小而增大,随球应力增大而减小,总体表现出随循环周次向体积收缩发展的变化规律,循环周次对累积体应变的影响较小;剪应变的发展受应力条件的影响较为显著,有效球应力减小时或增幅较缓,或在第1循环周次内突增,有效球应力增加时,剪应变增幅较缓;累积剪应变与初始应力比和试验过程中的动态应力比有关;土样可能存在类似临界状态线且处于其下方的“转折状态线”,当土样应力变化状态处于“转折状态线”与临界状态线之间的区域内时,土样状态将产生显著变化。  相似文献   

7.
三元乙丙橡胶(EPDM)作为一种高质量的绝缘材料,被广泛用于电缆接头的附件中,但其在电缆实际运行中承受较大的压力,这可能会影响绝缘性能。通过计算不同压力下EPDM中电荷输运的关键参数,如载流子迁移率的变化,研究压力对EPDM中电荷迁移的影响。通过设计单极载流子阻挡实验,并结合改进的电声脉冲法(PEA)测量设备,计算0.6~1.2 MPa(间隔0.2 MPa)范围内6种压力下EPDM中电子的迁移率。另外,通过跳跃电导模型对迁移率数据进行深入分析,发现在不同压力下EPDM中的迁移率没有显著变化,并且电子跃迁所需的能量和电子的跃迁距离也没有太大变化。结果表明:在电缆正常运行的工作环境下,压力不会影响EPDM的电气性能。  相似文献   

8.
An attempt is made to study the Einstein relation for the diffusivity–mobility ratio (DMR) in quantum wells (QWs) and quantum well wires (QWWs) of tetragonal compounds on the basis of a newly formulated electron energy spectrum taking into account the combined influences of the anisotropies in effective electron mass, the spin–orbit splitting, and the presence of crystal field splitting, respectively. The results for quantum-confined III–V compounds form a special case of our generalized analysis. The DMR has also been studied for QWs and QWWs of II–VI and IV–VI materials. Taking QWs and QWWs of CdGeAs2, InAs, CdS and PbSe as examples, it was found that the DMR increases with increasing carrier statistics and decreasing film thickness respectively in various oscillatory manners emphasizing the influence of dimensional quantizations and the energy band constants in different cases. An experimental method of determining the DMR in nanostructures with arbitrary dispersion laws has also been suggested and the present simplified analysis is in agreement with the suggested relationship. The well-known results for nanostructures with parabolic energy bands have also been obtained as special cases from this generalized analysis under certain limiting conditions.  相似文献   

9.
A comprehensive study of the intrinsic reliability of a 1.4-nm (equivalent oxide thickness) JVD Si3N4 gate dielectric subjected to constant-voltage stress has been conducted. The stress leads to the generation of defects in the dielectric. As a result, the degradation in the threshold voltage, subthreshold swing, gate leakage current, and channel mobility has been observed. The change in each of these parameters as a function of stress time and stress voltage is studied. The data are used to project the drift of a MOSFET incorporating JVD nitride at a low operating voltage of 1.2 V in 10 years. Based on these projections, we conclude that the increase in the Si3N4 gate dielectric leakage current does not pose a serious threat to device performance. Instead, the degradation in the threshold voltage and channel mobility can become the factor limiting the device reliability  相似文献   

10.
The effect of degeneracy both on the phonon-limited mobility and the effective mobility including surface-roughness scattering in unstrained and biaxially tensile strained Si inversion layers is analyzed. We introduce a new method for the inclusion of the Pauli principle in a Monte Carlo algorithm. We show that incidentally degeneracy has a minor effect on the bulk effective mobility, despite non-degenerate statistics yields unphysical subband populations and an underestimation of the mean electron energy. The effective mobility of strained inversion layers slightly increases at high inversion layer concentrations when taking into account degenerate statistics.  相似文献   

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