Crystal-field splittings of Er3+(4f11) in molecular beam epitaxially grown ErAs/GaAs

A detailed infrared-spectroscopic study is presented of the intra 4f-shell transitions 4I15/2→4I13/2 of Er3+(4f11), at λ=1.54 μm, in single-crystal ErAs films deposited on GaAs substrates by molecular beam epitaxy. Using Fourier-transform infrared absorption spectroscopy crystal-field splittings of both the 4I15/2 ground state and the first electronically excited state 4I13/2 are observed. Good agreement is found between the measured transition energies and those calculated for 4f11 ions in a crystal field of cubic (Oh) symmetry, as expected for the Er lattice site in unstrained ErAs. From the infrared absorption data, the relevant cubic fourth and sixth-order crystal field parameters are determined spectroscopically for the first time.