SiC/SiO_2界面粗糙散射对沟道迁移率影响的Monte Carlo研究

提出了一种SiC反型层表面粗糙散射的指数模型 ,并对 6H SiC反型层迁移率进行了单电子的MonteCarlo模拟 ,模拟中考虑了沟道区的量子化效应 .模拟结果表明 ,采用表面粗糙散射的指数模型能够使SiC反型层迁移率的模拟结果和实验值符合得更好 .模拟结果还反映出有效横向电场较高时表面粗糙散射的作用会变得更显著 ,电子的屏蔽效应降低了粗糙散射对沟道迁移率的影响 ,温度升高会引起沟道迁移率降低 .     

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     

不同散射机理对 Al2O3/InxGa1-xAs nMOSFET 反型沟道电子迁移率的影响

通过考虑体散射、界面电荷的库仑散射以及 Al₂O₃/In_xGa_1-xAs 界面粗糙散射等主要散射机理, 建立了以 Al₂O₃为栅介质In_xGa_1-xAs n 沟金属-氧化物-半导体场效应晶体管 (nMOSFETs) 反型沟道电子迁移率模型, 模拟结果与实验数据有好的符合. 利用该模型分析表明, 在低至中等有效电场下, 电子迁移率主要受界面电荷库仑散射的影响; 而在强场下, 电子迁移率则取决于界面粗糙度散射. 降低界面态密度, 减小 Al₂O₃/In_xGa_1-xAs 界面粗糙度, 适当提高In含量并控制沟道掺杂在合适值是提高 InGaAs nMOSFETs 反型沟道电子迁移率的主要途径. 关键词： InGaAs MOSFET 反型沟道电子迁移率 散射机理     

6H-SiC电子输运的Monte Carlo模拟

从实际测量和单粒子Monte Carlo模拟两个方面研究了6H-SiC的电子输运规律,在模拟中考 虑了6H-SiC主要的散射机理,模拟的结果体现了6H-SiC具有良好的高温和高场特性以及迁移 率的各向异性,其横向迁移率和纵向迁移率相差近5倍.模拟结果和实验数据的对比说明了对 6H-SiC输运特性的模拟是正确的. 关键词： 6H-SiC Monte Carlo模拟 迁移率 散射机理     

具有分形结构的SiC/SiO2界面的粗糙散射

用结构函数的方法建立了SiC粗糙表面的分形模型,用rms粗糙度Δ,分形维数D,以及相关长度L三个参量来刻画表面高度的自协方差函数,并提出了参数的计算方法.在此分形模型的基础上,能计算出SiC/SiO₂界面对沟道电子的粗糙散射.     

SiC电子霍耳迁移率的计算

基于对自身能带结构的分析以及各向同性弛豫时间近似法,采用三椭球等能面、抛物线性简化,建立了适于模拟n型6H-SiC电子霍耳迁移率和霍耳散射因子的解析模型,精确描述了不同散射机制对于6H-SiC低场电子输运特性的影响.计算结果与实测值有很好的一致性.     

高k栅介质小尺寸全耗尽绝缘体上锗p型金属氧化物半导体场效应晶体管漏源电流模型

通过求解沟道的二维泊松方程得到沟道表面势和沟道反型层电荷,建立了高k栅介质小尺寸绝缘体上锗(Ge OI)p型金属氧化物半导体场效应晶体管(PMOSFET)的漏源电流解析模型.模型包括了速度饱和效应、迁移率调制效应和沟长调制效应,同时考虑了栅氧化层和埋氧层与沟道界面处的界面陷阱电荷、氧化层固定电荷对漏源电流的影响.在饱和区和非饱和区,漏源电流模拟结果与实验数据符合得较好,证实了模型的正确性和实用性.利用建立的漏源电流模型模拟分析了器件主要结构和物理参数对跨导、漏导、截止频率和电压增益的影响,对Ge OI PMOSFET的设计具有一定的指导作用.     

小尺寸单轴应变Si PMOS沟道晶面/晶向选择实验新发现

小尺寸单轴应变Si p型金属氧化物半导体(PMOS)沟道反型层迁移率与晶面/晶向密切相关,应变PMOS优化设计时应合理选择沟道的晶面/晶向.目前,文献已有1.5 GPa应力强度下单轴应变Si PMOS沟道反型层迁移率按晶面/晶向排序的理论模型.然而,在器件实际制造过程中,覆盖SiN应力膜工艺是固定的,由于沟道弹性劲度系数具有各向异性,这样,不同晶面/晶向应变PMOS沟道所受应力强度不同,进而导致在实际工艺下沟道反型层迁移率晶面/晶向排序理论模型"失效".针对该问题,本文采用中国科学院微电子研究所40 nm工艺流程制备了不同晶面/晶向40 nm沟道小尺寸单轴应变Si PMOS与未应变Si PMOS,并通过器件转移特性测试,获得了小尺寸单轴应变Si PMOS反型层迁移率晶面/晶向排序结论.此有关小尺寸单轴应变Si PMOS沟道反型层迁移率晶面/晶向排序的相关结论,由于考虑了工艺实现因素,与文献理论预测排序结果相比,更适于指导实际器件制造;相关分析方法也可为其他应变材料沟道MOS相关问题的解决提供重要技术参考.     

高$lt;i$gt;k$lt;/i$gt;栅介质小尺寸全耗尽绝缘体上锗p型金属氧化物半导体场效应晶体管漏源电流模型

通过求解沟道的二维泊松方程得到沟道表面势和沟道反型层电荷, 建立了高k栅介质小尺寸绝缘体上锗(GeOI) p型金属氧化物半导体场效应晶体管(PMOSFET)的漏源电流解析模型. 模型包括了速度饱和效应、迁移率调制效应和沟长调制效应, 同时考虑了栅氧化层和埋氧层与沟道界面处的界面陷阱电荷、氧化层固定电荷对漏源电流的影响. 在饱和区和非饱和区, 漏源电流模拟结果与实验数据符合得较好, 证实了模型的正确性和实用性. 利用建立的漏源电流模型模拟分析了器件主要结构和物理参数对跨导、漏导、截止频率和电压增益的影响, 对GeOI PMOSFET的设计具有一定的指导作用. 关键词： 绝缘体上锗p型金属氧化物半导体场效应晶体管 漏源电流模型 跨导 截止频率     

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     

Effect of interface roughness on the carrier transport in germanium MOSFETs investigated by Monte Carlo method

Interface roughness strongly influences the performance of germanium metal--organic--semiconductor field effect transistors (MOSFETs). In this paper, a 2D full-band Monte Carlo simulator is used to study the impact of interface roughness scattering on electron and hole transport properties in long- and short- channel Ge MOSFETs inversion layers. The carrier effective mobility in the channel of Ge MOSFETs and the in non-equilibrium transport properties are investigated. Results show that both electron and hole mobility are strongly influenced by interface roughness scattering. The output curves for 50~nm channel-length double gate n and p Ge MOSFET show that the drive currents of n- and p-Ge MOSFETs have significant improvement compared with that of Si n- and p-MOSFETs with smooth interface between channel and gate dielectric. The $82\%$ and $96\%$ drive current enhancement are obtained for the n- and p-MOSFETs with the completely smooth interface. However, the enhancement decreases sharply with the increase of interface roughness. With the very rough interface, the drive currents of Ge MOSFETs are even less than that of Si MOSFETs. Moreover, the significant velocity overshoot also has been found in Ge MOSFETs.     

Low temperature electron mobility in Ga0.5In0.5P/GaAs quantum well structures

We analyse the low temperature subband electron mobility in a Ga_0.5In_0.5P/GaAs quantum well structure where the side barriers are delta-doped with layers of Si. The electrons are transferred from both the sides into the well forming two dimensional electron gas (2DEG). We consider the interface roughness scattering in addition to ionised impurity scattering. The effect of screening of the scattering potentials by 2DEG on the electron mobility is analysed by changing well width. Although the ionized impurity scattering is a dominant mechanism, for small well width the interface roughness scattering happens to be appreciable. Our analysis can be utilized for low temperature device applications.      

Remote polar phonon scattering for hot electrons in Si-inversion layers

The effect of the remote interfacial phonon (R.I.P.) scattering on the carrier drift velocity v is evaluated in function of the effective mobility, i.e. in function of the surface roughness. A perturbation theory using the experimental ν?F relation as a zero order approximation is used to calculate the contribution of the R.I.P. scattering. The calculation shows that the influence of this phonon mode scattering on the transport properties in Si-inversion layers is dependent on the carrier low field mobility and is of the order of 10%. The R.I.P. scattering is particularly significant in the warm electron regime, having no consequence on the saturation velocity.     

The effect of interface roughness scattering on low field mobility of 2D electron gas in GaN/AlGaN heterostructure

We report the results of our experimental and theoretical studies concerning the temperature dependence of electron mobility in a two dimensional electron gas (2DEG) confined at the GaN/AlGaN interface. Experimental mobility of about at 3.8 K remains almost constant up to lattice temperature , it then decreases rapidly down to about at . The results are discussed using a theoretical model that takes into account the most important scattering mechanisms contributing to determine the mobility of electrons in 2DEG. We show that the polar optical phonon scattering is the dominant mechanism at high temperatures and the acoustic deformation potential and piezoelectric scatterings are dominant at the intermediate temperatures. At low temperatures, the Hall mobility is confined by both the interface roughness (IFR) and ionised impurity scattering. The correlation length (Λ) and lateral size (Δ) of roughness at the GaN/AlGaN heterointerface have been determined by fitting best to our low-temperature experimental data.     

Electron mobility in a modulation doped AlGaN/GaN quantum well

We consider a two dimensional electron gas confined to a modulation doped AlGaN/GaN quantum well and study the dependence of low field mobility on various parameters such as composition, well width, remote impurity and interface roughness as a function of temperature. GaN is assumed to be in the zincblende structure. Acoustic and optical phonon, ionized remote impurity and interface roughness scatterings are taken into account in mobility calculations. The scattering rates are calculated using the self-consistently calculated wave functions obtained from the numerical solution of Poisson and Schr?dinger equations. Also found from the self-consistent solutions are the potential profile at the junction, the energy levels in the well and electron concentrations in each level. Ensemble Monte Carlo method is used to find the drift velocities of the two dimensional electrons along the interface under an applied field. The mobility of two dimensional electrons is obtained from the drift velocity of electrons. It is found that while remote impurity scattering is very effective for small values of spacer layer and doping concentrations, increasing Al concentration reduces the mobility of electrons. The effect of surface roughness, on the other hand, on mobility is almost independent of well width. The results of our simulations are compatible with the existing experimental data.     

On the role of scattering by surface roughness in silicon inversion layers

Experimental results are presented, which strongly suggest that scattering of carriers by surface roughness may be important in the silicon inversion layer of metal-oxide-semiconductor structures. Low temperature data for p-type channels on identical orientation at high surface field show that mobility results in this region are dependent only on the mode of sample preparation and are independent of surface charges. The most reasonable explanation for these observations is offered by a scattering mechanism which is closely associated with the surface condition of the SiSiO₂ interface, namely, scattering by surface roughness. This scattering is a direct result of the fluctuating potential caused by the imperfect interface which is only a small distance from the inversion carriers. A calculation of the effect of surface roughness on surface carrier mobility is also given and found to be in satisfactory agreement with the experimental results. The application of the theory to the observed results permits an estimate to be made of the physical dimensions of the surface roughness of the Si-SiO₂ interface.     

晶格匹配InAlN/GaN和InAlN/AlN/GaN材料二维电子气输运特性研究

文章研究了InAlN/GaN和引入AlN界面插入层形成的InAlN/AlN/GaN材料的输运性质. 样品均在蓝宝石上以脉冲金属有机物化学气相淀积法生长,霍尔迁移率变温特性具有典型的二维电子气(2DEG)特征. 综合各种散射机理包括声学形变势散射、压电散射、极性光学声子散射、位错散射、合金无序散射和界面粗糙度散射,理论分析了温度对迁移率的影响,发现室温下两种材料中2DEG支配性的散射机理都是极性光学波散射和界面粗糙度散射;AlN插入层对InAlN/GaN材料迁移率的改善作用一方面是免除2DEG的合金无序散射,另外还显著改善异质界面,抑制了界面粗糙度散射. 考虑到2DEG密度也是影响其迁移率的重要因素,结合实验数据给出了晶格匹配InAlN/GaN和InAlN/AlN/GaN材料的2DEG迁移率随电子密度变化的理论上限. 关键词： InAlN/GaN 二维电子气 迁移率     

Scattering of conduction electrons by interface roughness in semiconductor heterostructures

A fluctuation transport theory is applied to describe the mobility limiting effect of interface roughness scattering in semiconductor heterostructures. As an example we consider a high mobility transistor and compare electron scattering by interface roughness with Coulomb scattering processes by ions and dipole fluctuations. We show that the dynamical resistivity measurement provides detailed information about the autocorrelation of the interface morphology.