Erbium doping of molecular-beam epitaxially grown InSb on InP

Abstract

The transport properties of molecular-beam epitaxially grown InSb films doped with Er (atom densities NEr from 4.3×1016 cm−3 to 3.6×1020 cm−3) are reported at temperatures between 40 and 400 K. Er is a donor in InSb films grown under Sb to In flux ratios smaller than 1.1. At a flux ratio Sb/In=1.06, 25 atoms of Er give one extrinsic electron. The maximum extrinsic electron concentration achievable is ∼1.8×1017 cm−3, obtained for NEr≳4×1018 cm−3. Magnetoresistance measurements at 4.2 K show evidence for spin–disorder scattering of the electrons. The low-temperature (T<150 K) electron mobility increases with doping concentration up to rare-earth densities of 1×1018 cm−3; at higher rare-earth concentrations, the mobility decreases again. At room temperature, the mobility decreases monotonically with increasing Er concentration. We note the analogy between these results and the observations made on HgSe:Fe, a system in which the carrier mobilities might be enhanced by impurity charge ordering.