High-resolution optical absorption spectroscopy on Cr-related defects in GaAs and GaP

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Abstract
High-resolution optical absorption measurements on the 0.82 eV structure in GaAs(Cr) and on the 0.87 eV and 1.03 eV structures in GaP(Cr) are reported. The 0.82 eV absorption, attributable to an intra-centre Cr2+(5T2-5E) transition, which was previously reported as consisting of three lines, is resolved into seven thermalising components which can be fitted to the following scheme: three 5T2 ground state levels at energy 0, D and 4D with D=-(0.240+or-0.010) meV; five equally spaced spin-orbit-split 5E excited levels each separated by K=0.060+or-0.005 meV. The ground state is consistent with EPR results. For the analogous, though less well resolved, 0.87 eV absorption in GaP(Cr), D=-(0.20+or-0.03) meV and K<or approximately=0.05 meV. The 1.03 eV structure is due to a different Cr-related defect and a simple energy-level scheme is proposed to explain the main features of the spectrum.