OPTICAL-PROPERTIES OF SI PARTIALLY AMORPHIZED BY ION-IMPLANTATION

Optical properties of Si partially amorphized by As+-ion implantation have been studied by means of the two-phase mixture Bruggeman effective-medium approximation in which the partially amorphized layer is assumed as a physical mixture of fully amorphous Si and crystalline Si. The dielectric functions of the crystalline components deduced from this study differ appreciably from that of the bulk crystalline Si, especially in the vicinity of the sharp critical point (CP) features. We find that the change in the optical properties of the crystalline component is due to the increase in the broadening parameters of the CPs caused by implantation-induced damage. The amorphous volume fraction f(a) is also found to be simply expressed as f(a) = ([As+]/A)alpha, where [As+] is the ion fluence (150-keV As+ions), A (= 1 x 10(15) cm-2) is an amorphization-threshold fluence (i.e., the minimum fluence required to form a fully amorphous layer), and alpha (= 0.46) is an amorphization-rate factor of the incident ions. Dielectric-function-related optical data of partially amorphized Si, such as the complex refractive index, the absorption coefficient, and the normal-incidence reflectivity, are also presented as a byproduct of the present analysis.