**Semiconductors: theory and simulations**

A Theory Group in Crystallization Laboratory (NL-3) was actively involved in the investigations of semiconductors for number of years. Originally, this started by the thermodynamic investigations of mixed semiconductors, then evolved to simulations of properties of bulk crystals and structures to reach the stage of simulations of quantum structures and further, the optoelectronic and electronic devices.

Thermodynamic investigations included phase diagrams of III-nitrides and II-VI semiconductors, thermal properties of the nitrides. The theory used in the III-nitrides was based on real solution approximation for the mixed liquids (in the version used by Stringfellow) and Van Vechten scaling theory used for the mixed solid semiconductors. The results obtained include GaP-GaN phase diagrams and solubility curves. Also the *p-T* diagram of indium nitride (InN) was determined. In addition the experimental differential thermal analysis (DTA) investigations of *p-T* phase diagrams of II-VI compounds was made.

The theoretical investigations of the nitrides included also the spontaneous polarization, the piezoelectric effects and elastic properties of the nitrides. These properties were obtained using *ab initio* DFT calculations.

Ina addition to investigations of the bulk nitrides, the quantum structures based on these materials were investigated, mostly multiple quantum wells (MQWs). These investigations were also made using *ab initio* calculations of the system corresponding to the real systems at ambient and at high pressure. The obtained data were verified by time resolved photoluminescence (TRPL) measurements.

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