Interaction between Fe, dopants and secondary defects in MeV Fe ion implanted InP

We investigate the role of damage production and annealing in determining the Fe redistribution properties when implanting Fe at MeV energies in n-type InP. Fe ion implantation is performed at 2 MeV on ~100! InP substrates, both undoped and Sn doped (1.531018 cm23). Implants are performed both at room temperature ~RT! and at 200 °C ~HT!, with doses ranging from 131013 to 1.231015 cm22. A double implantation experiment is also performed, coimplanting Fe and P to investigate the influence of the P induced damage on the Fe redistribution/accumulation. Annealing is performed in the temperature range between 650 and 800 °C using flowing phosphine to prevent surface decomposition. To characterize the damage of our samples before and after annealing we employ Rutherford backscattering spectrometry in channeling condition and transmission electron microscopy; Fe depth profiles are measured by secondary ions mass spectrometry. A strict correlation is found between the position of Fe accumulation peaks and that of secondary defects formed in RT implanted samples during annealing; in particular it is shown that end of range dislocation loops and interfaces between damaged and undamaged crystal regions act as gettering sites for Fe atoms. The accumulation process is controlled by Fe diffusion that is greatly enhanced by the presence of mobile point defects related to the implantation damage; on the contrary it is shown that Sn doping has a strong retarding action on Fe diffusion. It is demonstrated that the strong reduction in damage production related to dynamic annealing in HT implantation can be used to reduce or avoid Fe redistribution/accumulation phenomena, leading to fairly stable implantation profiles also for high annealing temperatures and long annealing times.