Samarium doping of molecular-beam epitaxially grown InSb on InP

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We report here on the transport properties epitaxial InSb films grown by molecular-beam epitaxy and doped with Sm in the atom density range from 6.1×1016 cm−3 to 3.2×1018 cm−3 at temperatures between 40 and 400 K. Sm is a donor for InSb. The samples were grown at a flux ratio Sb/In=1.07±0.03. For Sm concentrations below 5×1017 cm−3, 25 atoms of Sm give one extrinsic electron. Samples grown with higher Sm concentrations have extrinsic electron densities around 1×1017 cm−3. At low temperatures (T<150 K), the electron mobility increases with doping concentration up to rare-earth densities of 3×1017 cm−3; at higher rare-earth concentrations, the mobility decreases again. At room temperature, the mobility decreases monotonically with increasing Sm concentration. Very similar results are observed on InSb films doped with Er. We point out that impurity charge ordering was invoked to explain similar observations made on HgSe:Fe.