Photoluminescence and optical characterization of a-Si(x)N(1-x): H based multilayers grown by PECVD

High room temperature photoluminescence efficiency (PLE) was observed for the first time in a-SixN1-x:H based nanometric multilayers deposited by plasma enhanced chemical vapour deposition (PECVD). The structure consists of alternate stoichiometric a-Si3N4:H barrier layers (E04=5.0 eV) and well layers in which E04 is varied between 2.11 eV and 2.64 eV. The peak of PL spectra and the absorption coefficient edge exhibits a blue shift up to 0.5-0.6 eV by decreasing the well thickness from 30 Å down to 5-10 Å. A strong increase in the PLE of multilayers, with well thickness around 5-10 Å, with respect to the PLE of bulk material was obtained. A p-i-n light emitting device (LED) with a multilayered structure as i-layer, having well layers with E04=2.64 eV and thickness 10 Å, is presented. The LED under forward bias shows an emission visible with the naked eye, with limited degradation after 8 hours of continuous operation.