OPTICAL STUDY OF SPIN-FLIP TRANSITIONS AT FE-3+ IN INP

The 0.5-eV (4000-cm-1) emission band in InP:Fe is studied in detail by Fourier-transform infrared photoluminescence (PL), time-resolved PL, and photoluminescence excitation (PLE) spectroscopy. We resolve new fi ne structures in both the zero-phonon (ZP) lines and in the correspond ing phonon sideband. The transient PL signal follows an exponential de cay with a time constant of 1.1 +/- 0.3 ms. The PLE shows that the 0.5 -eV band can be pumped via hole capture of Fe2+ and even more efficien tly by exciting resonantly the charge-transfer states [Fe2+ (5T2), h(b )], where the hole is bound to Fe2+. The results from PLE and the long decay time strongly support the interpretation of the 0.5-eV band as spin-flip transitions 4T1 --> 6A1 of Fe3+. We explain the fine structu re of the ZP lines by a dynamic Jahn-Teller distortion in the excited state 4T1. The decay of the charge-transfer states [Fe2+ (5T2), h(b)] leaves the Fe3+ ion in an excited state (Fe3+), which pumps the 0.5-e V emission.