Influence of strain relaxation in axial (In,Ga)N/GaN nanowire heterostructures on their electronic properties

TL;DR

This study investigates how elastic strain relaxation affects the electrostatic and electronic properties of axial (In,Ga)N/GaN nanowire heterostructures, revealing significant potential reduction and complex confinement effects.

Contribution

It provides a combined analytical and numerical analysis of strain and polarization effects in nanowire heterostructures, highlighting limitations in potential elimination and effects on electronic states.

Findings

Elastic relaxation reduces built-in electrostatic potential in nanowires.

Complete elimination of built-in potential is not achievable.

Strain and polarization potentials create complex confinement features.

Abstract

We present a systematic study of the influence of elastic strain relaxation on the built-in electrostatic potentials and the electronic properties of axial (In,Ga)N/GaN nanowire heterostructures. We employ and evaluate analytical and numerical approaches to compute strain and polarization potentials. These two ingredients then enter an eight-band k.p model to compute electron and hole ground states and energies. Our analysis reveals that for a sufficiently large ratio between the thickness of the (In,Ga)N disk and the diameter of the nanowire, the elastic relaxation leads to a significant reduction of the built-in electrostatic potential in comparison to a planar system of similar layer thickness and In content. However, a complete elimination of the built-in potential cannot be achieved in axial nanowire heterostructures. Nevertheless, the reduction of the built-in electrostatic potential leads to a significant modification of the electron and hole energies. Our findings indicate that the range of accessible ground state transition energies in an axial (In,Ga)N/GaN nanowire heterostructure is limited due to the reduced influence of polarization potentials for thicker disks. Additionally, we find that strain and polarization potentials induce complex confinement features of electrons and holes, which depend on the In content, shape, and dimensions of the heterostructure.