Overgrowth and strain in MBE-grown GaAs/ErAs/GaAs structures.

The molecular-beam epitaxial overgrowth of GaAs on single ErAs layers of varying thickness is studied, as well as the growth of, and strain accommodation in, ErAs/GaAs multilayer films on GaAs substrates. Resonant Raman scattering and Rutherford backscattering are used to characterize the crystal quality of overgrown GaAs layers, while Fourier-transform infrared absorption spectra of the crystal-field-split Er high 3+ intra 4f-shell transitions, at 1.54 mym, are exploited as a novel probe of strain accommodation in the ErAs layers. Overgrowth of GaAs of good crystal quality on ErAs, as well as growth of ErAs/GaAs multilayer structures, are both demonstrated, but only for ErAs layers less than about 5 monolayers in thickness. Such thin ErAs layers are found to be tetragonally distored due to elastic strain accommodation. Single buried ErAs films are found to be electrically continuous down to a thickness of 5 monolayers.