Optical study of spin-flip transitions at Fe3+ in InP.

Abstract

The 0.5-eV (4000-${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$) 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 fine structures in both the zero-phonon (ZP) lines and in the corresponding phonon sideband. The transient PL signal follows an exponential decay with a time constant of 1.1\ifmmode\pm\else\textpm\fi{}0.3 ms. The PLE shows that the 0.5-eV band can be pumped via hole capture of ${\mathrm{Fe}}^{2+}$ and even more efficiently by exciting resonantly the charge-transfer states [${\mathrm{Fe}}^{2+}$${(}^{5}$${\mathit{T}}_{2}$),${\mathit{h}}_{\mathit{b}}$], where the hole is bound to ${\mathrm{Fe}}^{2+}$. The results from PLE and the long decay time strongly support the interpretation of the 0.5-eV band as spin-flip transitions $^{4}$${\mathit{T}}_{1}$${\ensuremath{\rightarrow}}^{6}$${\mathit{A}}_{1}$ of ${\mathrm{Fe}}^{3+}$. We explain the fine structure of the ZP lines by a dynamic Jahn-Teller distortion in the excited state $^{4}$${\mathit{T}}_{1}$. The decay of the charge-transfer states [${\mathrm{Fe}}^{2+}$${(}^{5}$${\mathit{T}}_{2}$),${\mathit{h}}_{\mathit{b}}$] leaves the ${\mathrm{Fe}}^{3+}$ ion in an excited state (${\mathrm{Fe}}^{3+}$${)}^{\mathrm{*}}$, which pumps the 0.5-eV emission.