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Intraband absorption in self-assembled Ge-doped GaN/AlN nanowire heterostructures
M Beeler1, P Hille, J Schörmann
1CEA-CNRS Group Nanophysics and Semiconductors, CEA/INAC/SP2M and CNRS-Institute Néel, 17 rue des Martyrs, 38054 Grenoble cedex 9, France.
Nano Letters
|February 8, 2014
Summary
We observed infrared absorption in germanium-doped gallium nitride/aluminum nitride nanodisks within nanowires. The absorption shifts with germanium concentration and nanodisk thickness, influenced by strain and electronic structure.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Gallium nitride (GaN) and aluminum nitride (AlN) heterostructures are crucial for optoelectronic devices.
- Understanding intraband transitions in nanostructures is key to controlling their optical properties.
Purpose of the Study:
- To investigate the transverse-magnetic-polarized infrared absorption in Ge-doped GaN/AlN nanodisks (NDs) within GaN nanowires (NWs).
- To analyze the influence of Ge concentration, ND thickness, strain, and surface states on intraband transitions.
Main Methods:
- Experimental observation of infrared absorption spectroscopy.
- Theoretical calculations of band diagrams and electronic structures for GaN/AlN heterostructured NWs.
- Analysis of 3D strain distribution and surface state effects.
Main Results:
- Observed s-p(z) intraband absorption in Ge-doped GaN/AlN NDs.
- Absorption blue-shifted with increasing Ge concentration and red-shifted with increasing ND thickness.
- AlN shell induced compressive strain, blue-shifting interband transitions but minimally affecting intraband transitions.
Conclusions:
- Surface states deplete NW bases but do not fully screen polarization-induced electric fields.
- Free-carrier screening is critical for predicting photoluminescence.
- Many-body effects (exchange interaction, depolarization) blue-shift intraband transitions, overriding carrier screening effects.
