[en] Te-doped Si single crystals were successfully grown by the float zone technique with a doping concentration as high as 7 x 10¹⁶/cm³. The tellurium ionization level in silicon was investigated by both the temperature dependence of the Hall effect and by infrared absoprtion spectral measurements. Close agreement was found between these two techniques. The former shows a thermal activation energy for Si:Te of 0.20 eV, and the latter shows an optical activation energy of 0.1988 eV. The spacings and shapes of the excitation spectra for neutral Te donors in Si exhibits a close resemblance to that of other hydrogenic donor impurities in Si. The maximum absorption cross section for the Te ground-state: continuum transition is s/sub max/ = 1.4 x 10¹⁶ cm² at hn = 0.27 eV