Local structure around In atoms in coherently grown m-plane InGaN film

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Physics

Background:

• Indium Gallium Nitride (InGaN) is crucial for optoelectronic devices.
• Understanding the local atomic structure of InGaN is key to controlling its properties.
• M-plane InGaN films present unique structural characteristics compared to c-plane.

Purpose of the Study:

• Investigate the local atomic structure around Indium (In) atoms in m-plane InGaN.
• Analyze the effects of strain on interatomic distances within the m-plane InGaN film.
• Correlate the local structure with potential optical emission properties.

Main Methods:

• Polarization-dependent X-ray absorption fine-structure (XAFS) spectroscopy.
• Development of a step-by-step fitting procedure for m-plane wurtzite structures.
• Analysis of interatomic distances for In-N and In-Ga pairs along different crystallographic axes.

Main Results:

• First nearest neighbor In-N bond distances were found to be nearly isotropic.
• Second nearest neighbor In-Ga distances showed anisotropy, longer along the m-axis and shorter along the a-axis due to compressive strain.
• In-Ga distance along the c-direction elongated despite compressive strain, attributed to anisotropic m-plane structure.
• Local strain in the m-plane film was more relaxed than in c-plane InGaN quantum wells.
• Evidence of atomic localization for In atoms suggests potential for localized excitonic emission.

Conclusions:

• The local structure of In atoms in m-plane InGaN is anisotropic, deviating from simple strain models.
• Anisotropic atomic arrangements on the m-plane significantly influence interatomic distances, particularly along the c-direction.
• The observed atomic localization of In atoms indicates a strong potential for localized excitonic emission, similar to c-plane InGaN.