Production of semi-insulating layers in n-doped InP by Fe implantation

A detailed study of Fe implantation and damage annealing in indium phosphide is presented. The technological goal was to obtain thermally stable semi-insulating layers in n-type InP. Different characterization techniques were employed, including structural (x-ray diffraction, Rutherford backscattering spectrometry, and transmission electron microscopy), chemical (secondary ions mass spectrometry), and electrical (current-voltage) measurements. Both undoped and n-type (Sn) doped substrates were implanted with Fe doses ranging from 5x1011 to 2.2x1014 cm-2 and annealed at a temperature of 650 àC. The high doses used to compensate n+ doping caused amorphization of the material. The reordering process of the amorphous layers and its influence on the Fe redistribution properties were studied in detail. The activation of the implanted Fe atoms after annealing was derived. Although the recovery process of the amorphized layer appears to be rather complex, our results show that good crystal quality and full compensation can be reached also for n+ doped substrates, leading to resistivity values above 2x107 Ohm cm, even starting from an initial doping level as high as 1.4X1018 cm-3.