Possible excited states in Si:Se and Si:Te prepared by femtosecond-laser irradiation of Si coated with Se or Te film

•N+-N photodiodes were fabricated from Se- and Te-doped silicon.•We measured the I-V characteristics of Se- and Te-doped silicon n+-n photodiodes.•Te doped diode has better performance on photoelectric characteristics than Se doped diode.•Sub-bandgap photocurrent features are observed for Se- and Te-doped diodes.•The activation energies for Si:Se are in good agreement with the known Se levels Sec0(X1) and Se2+.