You are here : Home > L_Sim team > Modeling of the structural, electronic and optical properties of GaN/AlN nitride nanowires

Dulce Carolina Camacho Mojica

Modeling of the structural, electronic and optical properties of GaN/AlN nitride nanowires

Published on 25 May 2010


Thesis presented May 25, 2010

Abstract:
We have modeled the structural and electronic properties of nitride GaN/AlN nanowire heterostructures with atomistic simulation methods. We have first derived a Keating-like valence force field model for arbitrary wurtzite materials in order to compute the atomic positions and strain distribution in these heterostructures. With this model, we have been able to suggest the presence or confirm the absence of dislocations in various GaN/AlN nanowire heterostructures characterized by electron microscopy or X-Ray diffraction. We have then studied the electronic and optical properties of these nanostructures with the tight-binding method. We have been particularly interested in the effect of the internal electric field on GaN/AlN nanowires. Optical spectroscopy experiments have indeed evidenced a strong redshift of the luminescence of these nanowires (quantum confined Stark effect), due to the separation of the electrons and holes by the pyro- and piezoelectric field. This redshift is however smaller than measured in quantum wells and quantum dots with similar dimensions. To explain this, we have shown that it is essential to account for the screening of the electric field by the charges displaced by the latter, in particular from the surface states of the nanowire. We have proposed a simple analytical model to understand the main trends and help the design of nitride nanowire heterostructures.

Keywords:
Nanowires, nitrides, spontaneous polarization, piezoelectricity, Stark effect, tight-binding

On-line thesis.