Blue photo- and electroluminescence of silicon dioxide layers ion-implanted with group IV elements

The microstructural, optical and electrical properties of Si-, Ge- and Sn-implanted silicon dioxide layers were investigated. It was found, that these layers exhibit strong photoluminescence (PL) around 2.7 eV (Si) and between 3 and 3.2 eV (Ge, Sn) at room temperature (RT), which is accompanied by an UV emission around 4.3 eV. This PL is compared with that of Ar-implanted silicon dioxide and that of Si- and Ge-rich oxide made by rf magnetron sputtering. Based on PL and Fl, excitation (PLE) spectra we tentatively interpret the blue-violet PL as due to a T-1 --> S-0 transition of the neutral oxygen vacancy typical for Si-rich SiO2 and similar Ge- or Sn-related defects in Ge- and Sn-implanted silicon dioxide. The differences between Si, Ge and Sn will be explained by means of the heavy atom effect. For Ge-implanted silicon dioxide layers a strong electroluminescence (EL) well visible with the naked eye and with a power efficiency up to 5 x 10(-4) was achieved. The Fl, spectrum correlates very well with the PL one. Whereas the Fl, intensity shows a linear dependence on the injection current over three orders of magnitude, the shape of the Fl, spectrum remains unchanged. The I-V dependence exhibiting the typical behavior of Fowler-Nordheim tunneling shows an increase of the breakdown voltage and the tunnel current in comparison to the unimplanted material. Finally, the suitability of Ge-implanted silicon dioxide layers for optoelectronic applications is briefly discussed.