Hole Mobility Model Research Articles

A Wide Temperature Range Unified Undoped Bulk Silicon Electron and Hole Mobility Model

For decades, there is no unified model developed for Silicon carriers from 4K to above room temperature. In this paper, a unified undoped Silicon low field and high field mobility model for both electron in the <100> and <111> directions from 8K to 300K and 430K, respectively, and hole in the <100> direction from 6K to 430K is proposed and calibrated to the experiment. It is found that the Canali high field saturation model is sufficient to fit the <111> experimental data but not the <100> data due to the anisotropy-induced negative differential velocity. Therefore, a modified Farahmand model is used. To allow parameter interpolation in anisotropic simulation, the modified Farahmand model is also calibrated for the <111> direction. The model is then used to predict the mobility of electrons and holes in undoped Si at 4K, which can be served as the initial calibration parameters when reliable experimental data is available for the TCAD model development.

A Stress Response Model for Hole Mobility in the Inversion Layer of Ge MOSFETs

A Stress Response Model for Hole Mobility in the Inversion Layer of Ge MOSFETs

High spectral response of self-driven GaN-based detectors by controlling the contact barrier height

High spectral response of self-driven GaN-based ultraviolet detectors with interdigitated finger geometries were realized using interdigitated Schottky and near-ohmic contacts. Ni/GaN/Cr, Ni/GaN/Ag, and Ni/GaN/Ti/Al detectors were designed with zero bias responsivities proportional to the Schottky barrier difference between the interdigitated contacts of 0.037 A/W, 0.083 A/W, and 0.104 A/W, respectively. Voltage-dependent photocurrent was studied, showing high gain under forward bias. Differences between the electron and hole mobility model and the hole trapping model were considered to be the main photocurrent gain mechanism. These detectors operate in photoconductive mode with large photocurrent gain and depletion mode with high speed, and can extend GaN-based metal-semiconductor-metal detector applications.

Averaged hole mobility model of biaxially strained Si

We aim to establish a model of the averaged hole mobility of strained Si grown on (001), (101), and (111) relaxed Si1−x Gex substrates. The results obtained from our calculation show that their hole mobility values corresponding to strained Si (001), (101) and (111) increase by at most about three, two and one times, respectively, in comparison with the unstrained Si. The results can provide a valuable reference to the understanding and design of strained Si-based device physics.

A Low-Field Mobility Model for Bulk and Ultrathin-Body SOI p-MOSFETs With Different Surface and Channel Orientations

An easy-to-implement hole mobility model, which accurately predicts low-field mobility in bulk MOSFETs and ultrathin-body (UTB) silicon-on-insulator FETs with different crystal orientations, is developed. The model accounts for the influence of the surface orientation and the inplane current-flow direction on effective masses, subband repopulation, and scattering rates. The effects induced by extremely small silicon thicknesses are also addressed. A good agreement with the experimental mobilities of bulk and UTB FETs with silicon thicknesses from 60 nm to values as small as about 2.7 and 2.3 nm is demonstrated for devices with (100) and (110) substrates, respectively.

Mobility Modeling Considerations for Radiation Effects Simulations in Silicon

The results of semiconductor device simulations are highly dependent on the electron and hole mobility models. The manner in which mobility is modeled at high-injection levels is especially important for single-event upset simulations due to the large number of electron-hole pairs generated along a particle strike path. This paper presents an approach to modeling mobility that describes majority and minority carrier mobility, carrier-carrier scattering, and temperature dependence in a computationally efficient form relevant for radiation effects simulations in silicon.

Full-Band Monte Carlo investigation of hole mobilities in SiGe, SiC and SiGeC alloys

Hole transport properties in relaxed and biaxially strained Si 1- x Ge x , Si 1- y C y and Si 1- x- y Ge x C y alloys are investigated using a Full-Band Monte Carlo simulator. Our results allow the extraction of bulk, in-plane and out-of-plane hole drift mobilities. Doping effects in SiGeC alloys are taken into account through an efficient ionized-impurity scattering model. This model is based on inverse momentum relaxation times derived from phase-shift theory. 1 1 Also known as partial-wave theory. A new alloy scattering model relevant to the case of random ternary alloys is presented. It involves two effective alloy potential parameters, which account for the respective scattering strengths of Ge and C in the crystal lattice. From our mobility results we have derived an analytical hole mobility model which includes dependencies upon doping concentration, doping type, Ge content and C content.

Activation level in boron-doped thin germanium-on-insulator (GeOI): Extraction method and impact of mobility

We hereby present a non-destructive method for extracting the activation level on boron-doped germanium-on-insulator (GeOI) wafers, with a discussion on the impact of the hole mobility model. This method combines Monte Carlo boron profile simulations with optical Ge layer thickness T Ge and electrical sheet resistance R sh measurements. As B atoms are known not to diffuse in Ge for the usual activation temperatures (<800 °C), we can assume that the as-implanted dopant profile remains unchanged after annealing (no modelling of boron diffusion required). We highlight that the knowledge of the hole mobility dependence on activated impurities concentration in Ge is of paramount importance. Several experimental and theoretical models are available in the literature. After relative validity assessments, all of them have been implemented for extraction and unfortunately yield different values scattered over nearly one decade. Still, the lower-bound concentration 2.7×10 19 cm −3 is in the range of the state-of-the-art values for B-implanted crystalline Ge and has proven suitable for functional GeOI pMOSFET demonstration.

Physical modeling of hole mobility in silicon inversion layers under uniaxial stress

A physical model for hole mobility under either biaxial or uniaxial stress has been developed. The six-band k ⋅ p theory is used to obtain the bandstructure through stress-dependent Hamiltonian. The hole mobility in the silicon inversion layer is studied in details using Monte Carlo method. A numerically robust method has been applied to achieve self-consistent solution of Poisson’s and Schrodinger equations.

On the Influence of the Position-Dependence of Stress on Device Performance

We investigate the effect of the position-dependence of stress on device simulation in a 65 nm node technology using mechanical simulations for the stress created by a nitride liner in the n-MOSFETs and by SiGe source/drain pockets in the p-MOSFETs. For gate lengths below 0.1 μm, the difference in the linear and especially the saturation drain current becomes negligible when either considering the position-dependence of stress or using a constant stress picked from the source-side of the channel. In contrast, significant differences in the current enhancements exist for different mobility models (linear piezoresistance versus Intel hole mobility model) and different transport equations (drift-diffusion versus hydrodynamic).

A new hole mobility model for hydrodynamic simulation

A new self-consistent hole mobility model that includes the lattice and the hole temperature has been proposed. By including the lattice and hole temperatures as well as the effective transverse field and the interface fixed charge, the model predicts the saturation of the hole drift velocity and shows the effects of Coulomb scattering, surface phonon scattering, and surface roughness scattering. The model has been incorporated into a device simulation program, SNU-2D. The simulation results have been compared with the reported experimental data and the measured 0.1 μm pMOSFETs, and they are shown to agree quite well. The new model is expected to estimate the characteristics of very short-channel devices in the hydrodynamic model simulations.

An improved electron and hole mobility model for general purpose device simulation

A new, comprehensive, physically-based, semiempirical, local model for transverse-field dependent electron and hole mobility in MOS transistors is presented. In order to accurately predict the measured relationship between the effective mobility and effective electric field over a wide range of substrate doping and bias, we account for the dependence of surface roughness limited mobility on the inversion charge density, in addition to including the effect of coulomb screening of impurities by charge carriers in the bulk mobility term. The result is a single mobility model applicable throughout a generalized device structure that gives good agreement with measured mobility data and measured MOS I-V characteristics over a wide range of substrate doping, channel length, transverse electric field, substrate bias, and temperature.

On the understanding of electron and hole mobility models from room to liquid helium temperatures

The influence of the scattering processes on the mobility behavior in Si MOSFETs operated from room to liquid helium temperatures is studied. In particular, the role of the Coulomb and surface roughness mechanisms owing to Fowler-Nordheim stress and bulk bias effects is underlined. This enables us to propose reliable mobility models applicable in the room, liquid nitrogen and liquid helium temperature ranges and to enlighten the physical parameters which are hidden behind the analytical models. This modeling is very useful for the simulation of the MOSFET electrical properties under room and cryogenic operations.

A comprehensive model for inversion layer hole mobility for simulation of submicrometer MOSFET's

A comprehensive model of effective (average) mobility and local-field mobility for holes in MOSFET inversion layers is presented. The semiempirical equation for effective mobility, coupled with the new local-field mobility model, permits accurate two-dimensional simulation of source-to-drain current in MOSFETs. The model accounts for the dependence of mobility on transverse and longitudinal electric fields, channel doping concentration, fixed interface charge density, and temperature. It accounts not only for the scattering by fixed interface charges, and bulk and surface acoustic phonons, but it also correctly describes screened Coulomb scattering at low effective transverse fields (near threshold) and surface roughness scattering at high effective transverse fields. The model is therefore applicable over a much wider range of conditions compared to earlier reported inversion layer hole mobility models while maintaining a physically based character. >

Effective minority-carrier mobility in heavily doped silicon defined by trapping and energy-gap narrowing

A simple model for effective minority-carrier mobility in heavily doped silicon, lower than the extended-state (∼ majority-carrier) mobility, is developed based on the assumption that some of the carriers are trapped in band-tail (or shallow bound) states. The model demonstrates for the first time a correlation between measured mobility and energy-gap narrowing, which is also influenced by band tails. Numerical simulations of temperature-dependent hole transport in the emitters of n+-p-n transistors, which accurately predict the measured (base) currents when the effective hole mobility model and the energy-gap narrowing it implies are used, are discussed.

MOBILITY OF THE 2 D ADSORBED PHASESSTUDY OF THE MOBILITY OF AN HYPERCRITICAL TWO-DIMENSIONAL FLUID BY QUASI-ELASTIC NEUTRON SCATTERING

The adsorption of methane on a compressed form of exfoliated graphite (papyex) is characterized from a thermodynamical point of view by measuring a few adsorption isotherms. It is shown that the sample offers homogeneous (0001) surfaces and is well suited for neutron scattering studies. From the broadening of the incoherent neutron quasi-elastic peak, we are able to determine the diffusion coefficient of the two-dimensional hypercritical fluid of methane adsorbed on the graphite basal plane. We also measure its variation as a function of the coverage. The change in the diffusion coefficient is important, from 13 to 2.2 x 10-5 cm2 s-1 in the 0.45-0.9 coverage range and for T= 90 K, and consistent with a hole mobility model.