The erbium-impurity interaction and its effects on the 1.54 µm luminescence of Er3+ in crystalline silicon

We have studied the effect of erbium-impurity interactions on the 1.54 mm luminescence of Er³⁺ in crystalline Si. Float-zone and Czochralski-grown (100) oriented Si wafers were implanted with Er at a total dose of _~ 1X10¹⁵/cm². Some samples were also coimplanted with 0, C, and F to realize uniform concentrations (up to 10²⁰/cm³) of these impurities in the Er-doped region. Samples were analyzed by photoluminescence spectroscopy (PL) and electron paramagnetic resonance (EPR). Deep-level transient spectroscopy (DLTS) was also performed on p-n diodes implanted with Er at a dose of 6X10¹¹/cm² and codoped with impurities at a constant concentration of lXl0^l8/cm³. It was found that impurity codoping reduces the temperature quenching of the PL yield and that this reduction is more marked when the impurity concentration is increased. An EPR spectrum of sharp, anisotropic, lines is obtained for the sample codoped with 10²⁰ O/cm³ but no clear EPR signal is observed without this codoping. The spectrum for the magnetic field B parallel to the [100] direction is similar to that expected for Er³⁺ in an approximately octahedral crystal field. DLTS analyses confirmed the formation of new Er³⁺ sites in the presence of the codoping impurities. In particular, a reduction in the density of the deepest levels has been observed and an impurity+Er-related level at _~0.15eV below the conduction band has been identified. This level is present in Er+O-, Er+F-, and Er+C-doped Si samples while it is not observed in samples solely doped with Er or with the codoping impurity only. We suggest that this new level causes efficient excitation of Er through the recombination of e-h pairs bound to this level. Temperature quenching is ascribed to the thermalization of bound electrons to the conduction band. We show that the attainment of well-defined impurity-related luminescent Er centers is responsible for both the luminescence enhancement at low temperatures and for the reduction of the temperature quenching of the luminescence. A quantitative model for the excitation and deexcitation processes of Er in Si is also proposed and shows good agreement with the experimental results.