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Imaging Atomic-Scale Clustering in III-V Semiconductor Alloys.
Louise C Hirst1, Nicole A Kotulak1, Stephanie Tomasulo1
1U.S. Naval Research Laboratory , 4555 Overlook Ave. SW, Washington, DC 20375, United States.
ACS Nano
|March 14, 2017
Summary
Atomic-scale clustering was observed in Indium Aluminum Arsenic Antimonide (InAlAsSb) alloys, a key material for optoelectronics. This finding explains performance degradation in photovoltaic devices due to nonrandom compositional variations.
Area of Science:
- Materials Science
- Solid-State Physics
- Semiconductor Research
Background:
- Quaternary alloys are crucial for advanced optoelectronic devices.
- Immiscibility in alloys leads to phase segregation, degrading optical and electrical properties, especially in III-V photovoltaic cells.
- Indium Aluminum Arsenic Antimonide (InAlAsSb) is a promising material for high-bandgap subcells in multijunction solar cells.
Purpose of the Study:
- To investigate the atomic-scale structure and compositional variations in InAlAsSb alloys.
- To understand the root cause of performance degradation observed in previous studies of InAlAsSb.
- To confirm the presence of nonrandom compositional variations in multispecies alloys.
Main Methods:
- Quantitative scanning transmission electron microscopy (STEM) was employed.
- Atomic column intensity ratios were quantified from STEM images.
- Simulated images were used for comparison with experimental data.
Main Results:
- Direct observation of atomic-scale clustering in InAlAsSb.
- Quantification of intensity ratios confirmed nonrandom compositional variations.
- Experimental findings align with simulations, validating the observed clustering.
Conclusions:
- Atomic-scale clustering is a significant factor contributing to performance issues in InAlAsSb alloys.
- The study confirms nonrandom compositional variations in this multispecies alloy.
- Understanding and mitigating this clustering is essential for improving optoelectronic device performance.
