Rare earth doping of hydrogenated amorphous silicon alloyed with carbon

Abstract

Rare Earth(RE) doped carbon co-doped hydrogenated amorphous silicon films were prepared by electron cyclotron - plasma enhanced chemical vapor deposition of $SiH_4$ and $CH_4$ with concurrent sputtering of RE target. Increase in carbon concentration causes increase in optical band gap with out significant effect on structural disorder, resulting in improved $Er^{3+}$ photoluminescence intensity and reduced temperature quenching. Room temperature $Er^{3+}$ photoluminescence intensity was observed to increase fourfold in carbon doped film. However, low temperature and high resolution $Er^{3+}$ photoluminescence spectra has the same peak position and similar peak shape both for carbon doped and carbon free films. Low temperature pump power dependent $Er^{3+}$ PL intensity together with time resolved $Er^{3+}$ photoluminescence was analyzed using the rate equation for linear excitation rate. The result indicated that improvement in $Er^{3+}$ photoluminescence intensity in carbon doped film was mainly due to increase in luminescence efficiency. $Nd^{3+}$ photoluminescence observed for the first time from Nd doped carbon co-doped hydrogenated amorphous silicon was well described using the excitation and de-excitation through Nd-related state.