Diffusion of tellurium in silicon studied by the redistribution of an implanted source of radioactive 121Te

Abstract

Diffusion of tellurium in monocrystalline silicon was investigated in the temperature range 1149 K–1653 K. The radiotracer 121Te originated from production, on-line implantation and subsequent decay of its grandmother isotope 121Xe at the ISOLDE facility of CERN. Penetration profiles were measured by means of mechanical sectioning after long-time diffusion annealing. Te concentrations down to 10 16m −3 could be detected. An Arrhenius plot of the measured diffusivities reveals a pronounced curvature. This is interpreted in terms of two diffusion processes each of which is characterized by its own activation energy and pre-exponential factor. In the low temperature regime Te transport takes place through the vacancy (V) mechanism. Above about 1500 K, interstitial-substitutional diffusion becomes predominant. The latter component most probably arises from self-interstitials (I) participating via the kick-out reaction. From the present data the fractional V- pr I-component of Te diffusion under point-defect equilibrium can be calculated for any temperature.