Growth of αRh2As on GaAs (001) in a molecular-beam epitaxy system

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Abstract
Thin films of αRh2As were grown on top of GaAs (001) in a molecular‐beam epitaxy system by codeposition of rhodium and arsenic from separate sources. αRh2As is a good metal with a resistivity equal to 20 μΩ cm, suitable for electronic applications. The holes, the only type of carriers, have a concentration equal to 2.5×1022 cm−3, i.e., a value of the same order of magnitude as that of the best silicides. However, in spite of several features common to αRh2As and GaAs (symmetry, almost equivalent unit‐cell constant, and fcc As sublattices), the epitaxial arrangement [100](011)αRh2As//[110](001)GaAs mainly prevails instead of the expected simple unrotated relationship [100](001)αRh2As//[100](001)GaAs. This points out that the achievement of the minimum lattice mismatch is not always the driving force for the epitaxy. In agreement with the ternary phase diagram Rh‐Ga‐As, the (polycrystalline αRh2As)/GaAs system interacts above 400 °C and leads to the formation of the binary compounds RhGa and RhAs2.