共查询到19条相似文献,搜索用时 156 毫秒
1.
用Monte Carlo方法模拟闪锌矿相(zinc blende)ZnS电子的输运特性.实验采用的是非抛物线模型计算电子的能带结构,模拟包含了声学声子散射,极性光学声子散射,压电散射,电离杂质散射,能谷间散射以及自散射等散射机理.通过模拟得到了ZnS材料的平均漂移速度、平均电子能量随电场强度变化的曲线图,以及总散射率随电子能量变化图,并将结果与文献报道的模拟结果[1]进行比较得出:本实验方法具有模型简单,计算速度快,获得结果比较准确的优点. 相似文献
2.
报告了用全带MonteCarlo方法模拟纤锌矿相GaN和ZnO材料电子输运特性的结果.模拟所用的能带结构数据是用经验赝势法算得的.通过模拟得到了两种材料的平均漂移速度和平均能量与电场强度关系曲线,求得了电子迁移率.并且将两种材料的结果以及文献报道的GaAs的模拟结果进行了比较
关键词:
蒙特卡罗模拟
GaN
ZnO
输运特性
能带结构 相似文献
3.
应用全带多粒子Monte Carlo模拟方法,研究了钎锌矿相GaN 材料电子的高场输运特性. 模拟中利用了基于第一性原理总能量赝势方法计算得到的纤锌矿GaN的能带结构数据. 用Cartier的方法,计算碰撞电离散射率. 计算得到了电子平均漂移速度和电子平均能量与电场的关系曲线. 电离系数的分析表明当电场强度大于1 MV/cm时,才会有明显的碰撞电离发生,量子产额的分析表明当电子的能量大于7 eV时,量子产额随能量增加迅速增大. 研究了在0—4 MV/cm电场强度范围内电子在各导带的分布,低场下电子全部位于
关键词:
碰撞电离
高场输运
能带结构
Monte Carlo模拟 相似文献
4.
利用系综MonteCarlo法研究了2H ,4H和6HSiC的电子输运特性.在模拟中考虑了对其输运过程有着重要影响的声学声子形变势散射、极化光学声子散射、谷间声子散射、电离杂质散射以及中性杂质散射.通过计算,获得了低场下这几种不同SiC多型电子迁移率同温度的关系,并以4H SiC为例,重点分析了中性杂质散射的影响.最后对高场下电子漂移速度的稳态和瞬态变化规律进行了研究.将模拟结果同已有的实验数据进行了比较,发现当阶跃电场强度为10×106V·cm-1时,4H Sic电子横向瞬态速度峰值接近33×107cm·s-1,6H Sic接近30×107cm·s-1. 相似文献
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测量了多晶MgB2的热导,实验温区为5—300K.在双能隙模型下,用基于BCS超导理论的BRT热导理论对实验结果进行了分析,给出MgB2中两个能隙大小分别为16和51meV.对电子热导的分析结果表明σ能带准粒子受到的杂质散射远小于π能带准粒子受到的杂质散射.与单晶MgB2的热导实验结果相比,多晶MgB2的声子热导结果表明在c方向上热传导声子受到来自σ能带准粒子的散射,显示了MgB2在能量输运上的各向异性.
关键词:
MgB2
热导率
能隙 相似文献
8.
6H-SiC高场输运特性的多粒子蒙特卡罗研究 总被引:4,自引:3,他引:1
采用非抛物性能带模型,对6H-SiC高场电子输运特性进行了多粒子蒙特卡罗(Ensemble Monte Carlo)研究.研究表明:温度为296 K时,电子横向漂移速度在电场为2.0×104 V/cm处偏离线性区,5.0×105 V/cm处达到饱和.由EMC方法得到的电子横向饱和漂移速度为1.95×107 cm/s,纵向为6.0×106 cm/s,各向异性较为显著.当电场小于1.0×106 V/cm时,碰撞电离效应对高场电子漂移速度影响较小.另一方面,高场下电子平均能量的各向异性非常明显.电场大于2.0×105 V/cm时,极化光学声子散射对电子横向能量驰豫时间影响较大.当电场一定时,c轴方向的电子碰撞电离率随着温度的上升而增大.对非稳态高场输运特性的分析表明:阶跃电场强度为1.0×106 V/cm时,电子横向瞬态速度峰值接近3.0×107 cm/s,反应时间仅为百分之几皮秒量级. 相似文献
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利用非平衡格林函数方法研究了石墨纳米带中三空穴错位分布对热输运性质的影响.研究结果发现:三空穴竖直并排结构对低频声子的散射较小,导致低温区域三空穴竖直并排时热导最大,而在高频区域,三空穴竖直并排结构对高频声子的散射较大,导致较高温度区域三空穴竖直并排时热导最小;三空穴的相对错位分布仅能较大幅度地调节面内声学模高频声子的透射概率,而三空穴的相对错位分布能较大幅度地调节垂直振动膜高频声子和低频声子的透射概率,导致三空穴的相对错位分布不仅能大幅调节面内声学模和垂直振动模的高温热导,也能大幅调节垂直振动模的低温热导.研究结果阐明了空穴位置不同的石墨纳米带的热导特性,为设计基于石墨纳米带的热输运量子器件提供了有效的理论依据. 相似文献
11.
Using ensemble Monte Carlo simulation technique, we have calculated the transport properties of InN such as the drift velocity, the drift mobility, the average electron, energy relaxation times and momentum relaxation times at high electric field. The scattering mechanisms included scattering mechanisms are polar optical phonon, ionized impurity, acoustic phonon and intervalley phonon. It is found that the maximum peak velocity only occurs when the electric field is increased to a value above a certain critical field. This critical field is strongly dependent on InN parameters. The steady-state transport parameters are in fair agreement with other recent calculations. 相似文献
12.
The drift velocity, electron temperature, electron energy and momentum loss rates of a two-dimensional electron gas are calculated in a GaN/AlGaN heterojunction (HJ) at high electric fields employing the energy and momentum balance technique, assuming the drifted Fermi–Dirac (F–D) distribution function for electrons. Besides the conventional scattering mechanisms, roughness induced new scattering mechanisms such as misfit piezoelectric and misfit deformation potential scatterings are considered in momentum relaxation. Energy loss rates due to acoustic phonons and polar optical phonon scattering with hot phonon effect are considered. The calculated drift velocity, electron temperature and energy loss rate are compared with the experimental data and a good agreement is obtained. The hot phonon effect is found to reduce the drift velocity, energy and momentum loss rates, whereas it enhances the electron temperature. Also the effect of using drifted F–D distribution, due to high carrier density in GaN/AlGaN HJs, contrary to the drifted Maxwellian distribution function used in the earlier calculations, is brought out. 相似文献
13.
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. 相似文献
14.
Ozlem Celik Engin Tiras Sukru Ardali Sefer B. Lisesivdin Ekmel Ozbay 《Central European Journal of Physics》2012,10(2):485-491
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. 相似文献
15.
Bijaya Kumar Sahoo Sushanta Kumar Sahoo Sukadev Sahoo 《Journal of Physics and Chemistry of Solids》2013
We theoretically investigated the effect of macroscopic polarization (sum of spontaneous and piezoelectric polarization) on the thermal conductivity of wurtzite GaN. Macroscopic polarization contributes to the effective elastic constant of the GaN and thus modifies the phonon group velocity. We used the revised phonon velocity to estimate the Debye frequency and temperature. Different phonon scattering rates were calculated as functions of the phonon frequency. The thermal conductivity of GaN was estimated using revised parameters such as the phonon velocity and phonon relaxation rate. The revised thermal conductivity at room temperature increased from 250 to 279 W m−1 K−1 due to macroscopic polarization. The method we developed can be used for thermal budget calculations for GaN optoelectronic devices. 相似文献
16.
We have presented a theoretical study on electron resonant Raman scattering (ERRS) process associated with the bulk longitudinal optical (LO), surface optical (SO) and quasi-confined (QC) phonon modes in a free-standing wurtzite nanowire (NW). We consider the Fröhlich electron–phonon interaction in the framework of the dielectric continuum model. Numerical calculations on the GaN material reveal that differential cross-section (DCS) is sensitive to the wire size. The bulk LO and high-frequency quasi-confined (QC+) phonons make main contributions to the DCS and the impact of the SO phonon can be negligible in the ERRS process. Moreover, scattering intensity of the bulk LO phonon is strongly enhanced as the incident photon energy approaches the energy band-gap of the GaN. 相似文献
17.
Using rigorous kinetic treatment the steady state self-focusing of laser beams in a degenerate nonparabolic semiconductor (e.g. n-InSb) has been investigated beyond the perturbation limit. The nonlinearity arises due to the energy dependence of the electron mass in the conduction band. The energy loss of electron energy is assumed to be due to polar optical phonons and momentum transfer due to ionised impurity scattering/polar optical phonon scattering. It is found that nonlinearity in the dielectric constant or the self-focusing is more pronounced in the case of ionised impurity case as compared to polar optical phonon case. The effect of absorption is to suppress the self-focusing but the latter is also enhanced by degeneracy. 相似文献
18.
S. A. Ahmed 《Applied Physics A: Materials Science & Processing》2008,92(3):565-570
Thermoelectric power and electrical resistivity measurements on polycrystalline samples of Bi2Se3 and stoichiometric ternary compound in the quasi-binary system SnSe–Bi2Se3 in the temperature range of 90–420 K are presented and explained assuming the existence of an impurity band. The variation
of the electron concentration with temperature above 300 K is explained in terms of the thermal activation of a shallow donor,
by using a single conduction band model. The density of states effective mass m
*=0.15m
0 of the electrons, the activation energy of the donors, their concentration, and the compensation ratio are estimated. The
temperature dependence of the electron mobility in conduction band is analyzed by taking into account the scattering of the
charge carriers by acoustic phonon, optical phonon, and polar optical phonon as well as by alloy and ionized impurity modes.
On the other hand, by considering the two-band model with electrons in both the conduction and impurity bands, the change
in the electrical resistivity with temperature between 420 and 90 K is explained. 相似文献
19.
We present our experimental and theoretical studies regarding the energy and momentum relaxation of hot electrons in n-type bulk GaN and AlGaN/GaN HEMT structures. We determine the non-equilibrium temperatures and the energy relaxation rates in the steady state using the mobility mapping technique together with the power balance conditions as described by us elsewhere [N. Balkan, M.C. Arikan, S. Gokden, V. Tilak, B. Schaff, R.J. Shealy, J. Phys.: Condens. Matter 14 (2002) 3457]. We obtain the e–LO phonon scattering time of 8 fs and show that the power loss of electrons due to optical phonon emission agrees with the theoretical prediction. The drift velocity–field curves at high electric fields indicate that the drift velocity saturates at approximately 3×106 cm/s for the two-dimensional structure and 4×106 cm/s for the bulk material at 77 K. These values are much lower than those predicted by the existing theories. A critical analysis of the observations is given with a model taking into account of the non-drifting non-equilibrium phonon production. 相似文献