OPTICAL PROPERTIES AND VISIBLE ROOM TEMPERATURE PHOTOLUMINESCENCE OF AMORPHOUS SILICON RICH SILICON NITRIDE IN SiO₂/SiN_X QUANTUM WELL STRUCTURES

Two sets of multilayer structures consisting of 44 alternating layers of a-SiN_x:H (~ 4 nm and 6 nm) and SiO₂ (5 nm) have been fabricated using the plasma-enhanced chemical vapor deposition (PECVD) technique. The a-SiN_x:H that has a lower bandgap forms the well layer, while the large bandgap SiO₂ forms the barrier layer. A single bulk layer of a-SiN_x:H has also been grown to serve as a reference for comparison with the multilayer structures. The samples were studied using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), spectroscopic ellipsometry (SE), and photoluminescence (PL) techniques. The SE data have been successfully fitted, and the complex refractive indices of the a-SiN_x:H in the bulk and multilayers have been determined. The effects of quantum confinement on the optical bandgap and refractive indices of a-SiN_x:H have been investigated. The results are correlated to the PL spectra of the samples.