Study of Piezoelectricity on III/V semiconductors from atomistic simulations to computer modelling

Geoffrey Tse

Research output: ThesisDoctoral Thesis

Abstract

High quality and accurate computational data was obtained through first principle quantum mechanical calculations originated from density functional theory without the inclusion of empirical data (ab initio). The support of the computing facility NGS allows us to carry out our research involving large scale atomistic simulations. The data we recently obtained clearly shows piezoelectricity in GaAs and InAs are proved to be non linear in relation to a general strain.The high order fitting equation obtained through the parameterization procedure allowed us to directly evaluate higher order piezoelectric coefficients. By comparing with other linear and non linear models and also experimental data, we reached the conclusion that the validity of our model is correct in the limitation of small shear strain, particularly in case of (111) grown semiconductors. Such limitation however is not restricted under pseudomorphic growth in (001) direction where typically shear strain is small.We further validates our model through elasticity theory to demostrate the sign of the polarization is found to be opposite to bulk values for an InAs semiconductor layere grown in the (001) direction of growth and subject to 6-7% of lattice mismatch. This is additionally supported with experimental evidence (optical absorption spectra).Furthermore our model provides a direct way in evaluating the polarization for any crystal structure described on the atomic level. This is mainly beneficial to researchers who use molecular dynamics and empirical methods for predicting bandstructure.The fundamental performance for semiconductor devices can be improved through the use of the small polarization created from strain and is likely to bring advantages in future photovoltaics devices.
Original languageEnglish
Awarding Institution
  • The University of Manchester
Publisher
Publication statusPublished - 17 May 2012

Keywords

  • piezoelectricity, DFT, Kleinman, Polarity, Effective Charge, Zinc Blende

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