Jahn-Teller effect for Fe 2 + in III-V semiconductors

The Jahn-Teller coupling between local vibrations of the host III-V semiconductors and the electronic orbitals of ${\mathrm{Fe}}^{2+}$ 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 (${\mathit{E}}_{\mathrm{JT}}$). The compounds GaP:${\mathrm{Fe}}^{2+}$, GaAs:${\mathrm{Fe}}^{2+}$, and InP:${\mathrm{Fe}}^{2+}$ are fully discussed, especially the latter. Other III-V semiconductors such as GaSb:${\mathrm{Fe}}^{2+}$, InAs:${\mathrm{Fe}}^{2+}$, and InSb:${\mathrm{Fe}}^{2+}$ 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 ${\mathit{E}}_{\mathrm{JT}}$ are about 8 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ 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 ${\mathrm{Fe}}^{2+}$ as substitutional impurity is also performed.