Identifying Nanometer-scale Clustering in InAlAsSb Random Alloys Using Atom Probe Tomography

Semiconductor devices with enhanced efficiency, resilience, and/or optimized to specific applications/environments rely increasingly on the incorporation of III-V random alloys that have been engineered to possess certain required optoelectronic properties. When these materials are grown, however, challenges with non-random elemental arrangements can greatly affect – and in some cases eliminate – realization of the desired optoelectronic behavior. Multijunction photovoltaic devices represent a case in point. As efficiencies are pushed to break the 50% mark, the system of III-V materials lattice-matched to InP, with available direct bandgaps of 0.74-1.8 eV, nominally provide a near-ideal bandgap combination for triple-junction (3J) devices [1], [2]. The top junction under consideration for this system is the InAlAsSb random alloy, due to its theoretically predicted maximum bandgap of 1.74 eV.