Implant and characterization of highly concentrated Fe deep centers in InP

High temperature (> 200 degreesC) Fe ion implantation in combination with a post-implantation annealing treatment is used to introduce a high active Fe concentration, well above the solubility limit, in n-InP. Current-voltage (I-V) characteristics and photo-induced current transient spectroscopy (PICTS) experiments reveal that a strong increase of the Fe2+ concentration is reached with respect to the equilibrium values, with a limited fraction (of the order of 10%) of the implanted Fe being activated and a strong dependence of the Fe2+ concentration on the substrate doping density. Proton induced X-ray emission spectroscopy (PIXE) and X-ray absorption fine structure (XAFS) measurements were carried out in order to analyze the local structural environment of the implanted Fe atoms in the host InP lattice. The results indicate that most of the Fe atoms resides on non-substitutional sites after annealing, most likely in Fe-P agglomerates. These structures, however, do not show any detrimental effects on the Fe2+-related electrical and optical properties.