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Strain Driven Shape Evolution of Stacked (In,Ga)N Quantum Disks Embedded in GaN Nanowires
Javier Bartolomé1, Michael Hanke1, David van Treeck1
1Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany.
Nano Letters
|July 25, 2017
Summary
Fabricating uniform nanowire quantum disks is challenging. This study reveals disk shape changes are predictable, driven by strain relaxation, not radial growth, enabling controlled design.
Area of Science:
- Semiconductor Nanostructures
- Materials Science
- Quantum Engineering
Background:
- Achieving homogeneous size and shape distribution in stacked nanowire quantum disks is crucial for narrow light emission bandwidth.
- Observed changes in disk shape along the stacking direction have been a persistent challenge in nanowire fabrication.
Purpose of the Study:
- To investigate and explain the systematic changes in the shape of stacked (In,Ga)N quantum disks within GaN nanowires.
- To develop a model that accounts for the observed shape evolution during nanowire growth.
Main Methods:
- High-resolution transmission electron microscopy (HR-TEM) to analyze the physical structure of stacked quantum disks in nanowires.
- Finite element method (FEM) calculations to model strain distribution and its effect on disk shape.
- Development of a simple physical model based on energy minimization principles.
Main Results:
- Demonstrated that radial nanowire growth is negligible and does not cause shape changes in the quantum disks.
- Identified strain relaxation of the active region as the primary cause for the systematic change in disk shape along the stacking direction.
- Proposed a model where cumulative strain effects lead to progressively smaller aspect ratios in successive quantum disks.
Conclusions:
- Strain relaxation is a critical factor governing the shape evolution of quantum disks in nanowires.
- The developed model accurately predicts the observed shape changes, offering insights for designing controlled nanostructures.
- These findings are essential for optimizing the fabrication of multiquantum disks for applications requiring narrow light emission bandwidth in lattice-mismatched nanowire systems.
