Atomistic Modelling

Description

Tyndall has extensive and unique experience in the atomistic calculation of the physical parameters that determine optical, electronic transport and thermoelectric properties of materials for novel devices. Modelling/Data Sets include the electronic and vibrational states, band offsets, electron-phonon coupling, deformation potentials, alloy and impurity scattering, optical matrix elements and oscillator strengths. The expertise at Tyndall ranges from the determination of these properties in bulk materials to assessing how they change due to alloying, nanostructuring and when in contact with novel materials as used in disruptive devives. Examples include the electronic thermoelectric properties of group IV alloys and nanostructures, such as SiGe and Si nanowires; optical and transport properties and band offsets in group IV – III-V heterostructures, such as Ge/InGaAs and related alloys, and electronic and vibrational dynamics in semiconductors, metals and semimetals. Our atomistic approach has the added advantage of allowing access to both quantum and classical properties, and have led to improved materials for nanoelectronic, ultrascaled, quantum and optical devices.

Tyndall provides modelling access to the determination from first-principles of:

Effects of strain, doping and alloying on the electronic and thermoelectric of group IV materials, including electron-phonon, impurity and alloy scattering.
Band offsets between group IV, group-III and group-V materials, and their dependence on strain and anion/cation interface termination.
Deformation potentials as a function of strain and alloy composition for group-IV compounds and Si nanowires.
Optical matrix elements between electronic bands in group-IV and group III-V alloys, and superlattices. This includes optical coupling between indirect bands via electron-phonon, impurity and alloy scattering.
Electron and phonon non-equilibrium dynamics, for instance after photoexcitation, in Ge and Bi
Effects of alloying and strain on phonon band structures.
Simulation of the diffuse X-Ray scattering signal.

Specifications

Based on group IV, group-III and group-V materials and their alloys. We assist in the evaluation/control of interactions between spins, photons and phonons. Tyndall has experience calculating the effects of intrinsic defects in group IV semiconductor nanostrucures on the band structure, optical oscillator strengths, spin and transport properties. These are currently being studied for single photon sources for quantum cryptography, thermoelectric and optical properties.

Ascent+ facility
Tyndall

Platform Technology

Nano for Quantum Technologies

Key Enabling Capability

Modelling / Databases

Case Studies

Calculation and experimental demonstration of light emission in direct-band Ge

First-principles calculation of band offsets between Ge/III-V alloys
Calculation of the effects of strain and quantum confinement on emission wavelength
Calculation of PL spectra in bulk and nanostructured strained Ge with/without defects

Prediction of giant mobility in highly strained Ge

First-principles calculation of the electron-phonon and alloy limited mobility in Ge nanostructures

Prediction of 50% thermoelectric efficiency increase in SiGe under strain

First-principles calculation of the electron-phonon and alloy limited current density, Seebeck coefficient, Lorenz factor, thermal conductivity in strained SiGe alloys as a function of Temperature and doping concentration. Including thermal effects on band-structure.

Prediction of the giant piezoresistance effect in SiGe

First-principles calculation of the electron-phonon and alloy limited piezoresistive parameters in SiGe

First-principles calculation of the diffuse X-Ray scattering in Ge
Calculation of the time-dependent non-equilibrium distribution of electrons and phonons
Excellent prediction of experimental results

Publications