Time-dependent photoluminescence of InP:Fe

Abstract

The time dependence of the ${}_{}{}^5{}_{}{}^{}T_2^{}{}_{}{}^{}\to {}_{}{}^5{}_{}{}^{}E$ photoluminescence transition of ${\mathrm{Fe}}^{2+}$ in InP has been measured as a function of temperature for a well-characterized series of Fe-doped samples ranging from $n$ type to semi-insulating. The observed time dependences can be fitted over a wide range of temperatures by a relatively simple model that accounts for the relaxation of the system back to the equilibrium (dark) condition. The magnitude of the low-temperature electron capture cross section by the neutral ${\mathrm{Fe}}^{3+}$ center (${\sigma }_n>5\mathrm{}\times {10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$ at 5 K) was found to be much larger than expected and exhibited a marked decrease with increasing temperature up to 29 K. This has been interpreted in terms of a two-step capture process involving a shallow level. The low-temperature capture cross section for holes (${\sigma }_p\approx 2\times {10}^{-17\mathrm{}}$ ${\mathrm{cm}}^2$) and the lifetime of the ${}_{}{}^5{}_{}{}^{}T_2^{}{}_{}{}^{}\to {}_{}{}^5{}_{}{}^{}E$ excited state (${\tau }_0\approx 11$ μsec) were also determined. The latter quantity decreases dramatically with temperature due to ${}_{}{}^5{}_{}{}^{}T_2^{}{}_{}{}^{}\to {}_{}{}^5{}_{}{}^{}E$ multiphonon relaxation. It was also determined that an Auger process recently discussed by Langer can be important during the exciting pulse in inducing ${}_{}{}^5{}_{}{}^{}T_2^{}{}_{}{}^{}\to {}_{}{}^5{}_{}{}^{}E$ nonradiative transitions.