Visible photoluminescence from low temperature deposited hydrogenated amorphous silicon nitride

Hydrogenated amorphous silicon nitride (a-SiNx:H) samples have been prepared by plasma enhanced chemical vapor deposition (PECVD) using a mixture of silane (SiH4), nitrogen and ammonia (NH3). Most films exhibit visible photoluminescence (PL) and some emit strong PL after annealing. While films grown without NH3 exhibit PL in the deep red, those grown with NH3 show PL in the green. The PL properties of these films with no oxygen (O) content are similar to those of silicon oxide (SiOx) films and porous Si. Using infrared and X-ray Photoelectron Spectroscopy, we suggest that PL from a-SiNx:H films originate from Si clusters which form during PECVD and crystallize upon annealing. We propose that the presence of O is not necessary for efficient PL.