Jahn-Teller effect for Fe2+ in III-V semiconductors

The Jahn-Teller coupling between local vibrations of the host III-V semiconductors and the electronic orbitals of Fe2+ substitutional impurities are studied from a theoretical point of view. Coupling to both multiplets resulting after crystal-field splitting is considered. Calculations are performed with just one adjustable parameter, namely, the Jahn-Teller energy (𝐸JT). The compounds GaP:Fe2+, GaAs:Fe2+, and InP:Fe2+ are fully discussed, especially the latter. Other III-V semiconductors such as GaSb:Fe2+, InAs:Fe2+, and InSb:Fe2+ are referred to for particular applications of the model. The results for the lower multiplet show good agreement for the predicted lines with luminescence spectra; the coupling phonon is identified as belonging to the points TA(L) of the Brillouin zone; values for 𝐸JT are about 8 cm−1 for this coupling. The coupling to the upper multiplet is described in terms of upper limits as the available infrared-absorption spectra do not show evidence for more than one zero-phonon line. A comparison with similar calculations for II-VI compounds with Fe2+ as substitutional impurity is also performed.