Atomic-Scale Structure of Random Solid Solutions: Extended X-Ray-Absorption Fine-Structure Study ofGa1−xInxAs

In random solid solutions of ${\mathrm{Ga}}_{1-x}{\mathrm{In}}_x\mathrm{As}$, the Ga-As and In-As near-neighbor distances change by only 0.04 Å as $x$ varies from 0.01 to 0.99, despite the fact that this alloy accurately follows Vegard's law, with a change in average near-neighbor spacing of 0.17 Å. This result contradicts the underlying assumption of the virtual-crystal approximation. Nonetheless, the cation sublattice approaches a virtual crystal with a broadened single distribution of second-neighbor distances, whereas the anion sublattice exhibits a bimodal anion-anion second-neighbor distribution.