Imaging Atomic-Scale Clustering in III–V Semiconductor Alloys

Quaternary
alloys are essential for the development of high-performance
optoelectronic devices. However, immiscibility of the constituent
elements can make these materials vulnerable to phase segregation,
which degrades the optical and electrical properties of the solid.
High-efficiency III–V photovoltaic cells are particularly sensitive
to this degradation. InAlAsSb lattice matched to InP is a promising
candidate material for high-bandgap subcells of a multijunction photovoltaic
device. However, previous studies of this material have identified
characteristic signatures of compositional variation, including anomalous
low-energy photoluminescence. In this work, atomic-scale clustering
is observed in InAlAsSb via quantitative scanning
transmission electron microscopy. Image quantification of atomic column
intensity ratios enables the comparison with simulated images, confirming
the presence of nonrandom compositional variation in this multispecies
alloy.