Formation of Mn-Related Defect Band in InP

Electron paramagnetic resonance, optical absorption, luminescence and electrical studies of InP highly doped with Mn were performed. Electron paramagnetic resonance revealed presence of manganese in Mn2+ (d(5)) configuration. In optical absorption, systematic reduction of InP band gap was observed with increase in Mn content. This was correlated with increase in photoionization-type absorption band starting at 0.2 eV. Time-resolved photoluminescence measurements showed decrease in photoexcited carrier lifetime and shortening of donor-acceptor pair recombination time with increase in Mn content. Moreover, photoluminescence band was shifted to lower energies, similarly to optical band gap. In electrical transport two mechanisms of conductivity were observed. Valence band transport dominated at higher temperatures, above 160 K, and activation energy of free-hole concentration was determined as about 0.20 eV. At lower temperatures hopping conductivity, clearly related to Mn defect band, was present. All these results were consistent with assumption of creation of Mn-related defect-band at 0.2 eV above InP valence band. It was found that Mn centers responsible for this band were in configurations of either d(5) or d(5) plus a hole localized about 7 Angstrom around corresponding Mn core.