Time-dependent photoluminescence of InP:Fe

The time dependence of the ⁵T₂→⁵E photoluminescence transition of Fe²⁺ 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 Fe³⁺ center (σₙ>5×10^-16 cm² 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 (σₚ≈2×10^-17 cm²) and the lifetime of the ⁵T₂→⁵E excited state (τ₀≈11 {μ}sec) were also determined. The latter quantity decreases dramatically with temperature due to ⁵T₂→⁵E multiphonon relaxation. It was also determined that an Auger process recently discussed by Langer can be important during the exciting pulse in inducing ⁵T₂→⁵E nonradiative transitions.