Modulation of the photoluminescence spectrum by depth selective excitation of an embedded Si-nc layer

Silicon nanocrystals (Si-nc) were produced by the implantation of Si+ in excess into amorphous quartz and a 1 mum SiO2 film thermally grown on an Si substrate. In the latter, the photoluminescence (PL) spectra from the Si-nc, induced by Ar+ laser excitation, are modulated by Fabry-Perot type interference fringes due to the interference of the emitted light reflected at the Si/SiO2 interface with that propagating directly towards the surface. In this paper, we investigate the spectral modulation and the PL as a function of the incidence angle of the pump laser and the Si+ dose implantation. The modulation of the PL spectra is influenced by the distribution in depth of the pump laser intensity in the SiO2 layer, the depth distribution of the Si-nc and the refractive index distribution of the layered structures. One goal of our work is to modulate the emission spectra by acting on the thickness of the SiO2 layer. Simulations have been undertaken to establish a relation between the modulation of the PL spectrum and the depth distribution of both the pump laser intensity and the Si-nc. This study required the precise measurements of the depth distribution of both the complex refractive index (n, k) by ellipsometry and the Si-nc by transmission electron microscopy (TEM).