Study of ErAs/GaAs strained-layer structures using optical absorption and ion channeling

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Abstract
The crystal‐field splittings recently observed in the Er‐related optical absorption spectra of ErAs films grown on GaAs by molecular‐beam epitaxy are further investigated with respect to their applicability in characterizing strain accommodation in ErAs/GaAs multilayer structures. Rutherford backscattering axial channeling measurements are used to directly assess strain accommodation in the epitaxial films. The crystal‐field splittings observed in room‐temperature absorption spectra of samples containing thick strain‐relieved ErAs layers are consistent with the cubic (Oh) symmetry expected for the Er lattice site in unstrained ErAs. In sharp contrast, a multilayer structure containing two‐monolayer‐thick, coherently strained ErAs layers shows pronounced changes in the energies, linewidths, and relative intensities of the crystal‐field‐split spectral lines, as well as the appearance of additional weak absorption lines. This behavior is attributed to strain‐induced distortion of the crystal field in which the rare‐earth ions reside. The relative influence of hydrostatic and uniaxial strain components on the optical spectra is discussed.