WEAK JAHN-TELLER COUPLING OF IRON (FE2+) IN INP, GAAS AND GAP ZEEMAN AND PIEZOSPECTROSCOPY

We report on Zeeman and piezospectroscopic investigations on the well known intense photoluminescence emission of iron (Fe2+) in the m-V com pound semiconductors InP, GaAs and GaP. The optical FTIR measurements allowed all Zeeman components of the sharp transitions 1 and 2 to be c learly resolved. Pure crystal field calculations within the D-5 term ( E-5, T-5(2)) Of Fe2+ cannot fully explain the spacings of zero-phonon lines and the Zeeman splitting. These discrepancies indicate a weak Ja hn-Teller effect in the ground state E-5. The coupling of epsilon vibr ational modes to the E-5 State is calculated explicitly in the direct product space (epsilon x E-5) + T-5(2), where the mixing of ground and excited states comes from spin-orbit interaction. The model is a one- phonon approximation which is discussed on the background of calculati ons [1] that estimate the relevant vibrational modes out of the entire phonon spectrum. The piezospectroscopic data show only a weak Jahn-Te ller effect to take place in the excited 5T(2) state, too.