Phonons in Semiconductors
One of the main challenges in ultra-scaled semiconductor devices is the flow of heat. In order to understand that efforts are going on in the group. In this direction calculation of phonons in different materials and using phonons for thermal transport is going on.
The phonons in zinc-blende and wurtzite semiconductors are modeled using the modified Valence Force Field (MVFF) method. The details about the theory of this model is given on this page
An important step for work in this direction was the benchmarking of the model with experimental data. In this regard efforts are going on in the group. Some of the results at are glance are shown here.
- Benchmarking bulk phonons in Si and Ge.
We have benchmarked the phonon dispersion in relaxed and strained bulk zinc-blende materials. The details of this work and other related items can be found in this paper
The experimental results are well benchmarked using this model
- Phonons under strain
Phonons in semiconductors also respond to pressure. This response is noted experimentally in terms of the phonon frequency shifts given by the parameter called mode Gruneisen Parameter. This is defined as:
The Figure below shows the matching of the experimental and simulated Gruneisen Parameter.
Other Efforts in phonon modeling:
There are other efforts in the group going on to develop the MVFF model for other materials too. For the optimization of the material parameters Genetic Algorithm is used. The kind of physical parameters to be matched are also determined.
Group member involved:
- Kai Miao: Phonon dispersion in Bandstructure Lab
- Abhijeet Paul: Phonon model and applications of phonons to thermal transport, thermoelectricity and Raman spectroscopy.
- Sebastian Steiger: Phonon modeling in NEMO5. Optimization and extension of MVFF model to III-Vs and Wurtzite.
- Mathieu Luisier: Phonon modeling, thermal transport and electron-phonon interaction.
- Mehdi Salmani: Utilization of Genetic algorithms to optimize phonon parameters.
- Denis Areshkin