Structural,electrical and optical characterization of singlecrystal ErAs layers grown on GaAs by MBE

A detailed study is presented of the structural, electrical, and optical properties of ErAs films grown on GaAs by molecular beam epitaxy (MBE). ErAs layers 1500Å thick were grown successfully over a relatively wide range of substrate temperatures (420-580° C), although overgrowth of GaAs on ErAs was found to be difficult. In-situ reflection highenergy electron diffraction (RHEED), x-ray diffraction, and Rutherford backscattering (RBS) measurements all indicate single crystal growth. Analysis of X-ray rocking curves reveals that, over the range of substrate temperatures studied, strain due to the lattice mismatch between ErAs and GaAs is completely inelastically relieved in the 1500Å thick ErAs layers. Variable-temperature Hall measurements reveal metallic behaviour in all samples, with no pronounced dependence on substrate temperature. Spectrally narrow (0.6 meV) intra 4f-shell transitions of Er³⁺ (4f¹¹), at 1.54 μm, have been observed in ErAs epitaxial layers both in absorption (by Fourier transform infra-red spectroscopy, FTIR) and in emission (by cathodoluminescence). The crystal-field splittings observed in the FTIR spectra are consistent with the cubic(O _h)symmetry expected for the Er lattice site in unstrained ErAs, in good agreement with the x-ray analyses.