ICAMS / Interdisciplinary Centre for Advanced Materials Simulation
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First-principles study and thermodynamic modelling of foreign impurities and native defects in GaAs

Date: 05.05.2016
Place: EMRS Spring Meeting, Lille, France

Masoomeh Ghasemi, Department of Physics, Lund University, Lund, Sweden
Suzana Fries
Martin Stankovski, Lund University, Lund, Schweden
Jonas Johansson, Materials Science Nanoenergy, Lund Universtity, Lund

III-IV semiconductor nanowires are promising building blocks of future electronic and optoelectronic devices. The nanowires are often doped with foreign impurity atoms to tune their electronic properties. In addition to this, native defects such as vacancies, interstitials and anti-sites may also form unintentionally. Moreover, during the growth of Au-seeded nanowires, Au impurities may also incorporate in the semiconductor. The aim of the current project is to study the energetics and concentrations of variety of native defects and foreign impurity atoms in the GaAs nanowires. We are calculating the formation energy of different point defects in GaAs including the Zn dopant, Au impurities and vacancies in different charged states through Density Functional Theory (DFT) calculations. Then, based on the relative stability of the defects, we will set up a thermodynamic model for the GaAs compound using a methodology which combines phase diagram and thermochemical experimental and first-principles information, so called CALPHAD method [1]. As a result of the current study, the existing thermodynamic model of the GaAs phase which does not take the impurity and native defect concentrations into account will be optimized. This model can eventually be used for modelling the growth of Zn-doped and Au-seeded GaAs nanowires [2].

[1] H.L. Lukas et. al., Computational thermodynamics: The Calphad method. Cambridge University Press 2007.

[2] Yang et. al., J. Cryst. Growth, 414 (2015), 181.

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