Improved Photoluminescence Intensity of Silicon Rich Oxide Film by Surface Etching

Silicon rich oxide (SRO) films are a promising material to develop silicon-based light sources, a key device in Silicon Photonics. Nevertheless, it has been experimentally shown that a surface oxide layer is formed on the SRO films after a thermal annealing process, which possibly does not contribute to light emission. Then, in this work, the effect of wet etching steps (different depths) on the morphological and photoluminescent (PL) properties of SRO films is studied. Two SRO films with different Si-excess, labeled as SRO
5
and SRO
10
, were deposited by low pressure chemical vapor deposition (LPCVD) using N
2
O and SiH
4
as the reactive gasses. Subscript 5 and 10 indicates the gas flow ratio (Ro)=N
2
O/SiH
4
. The initial thickness of both SRO films is about 80 nm. An improvement of the PL intensity is observed when the thickness of SRO
10
and SRO
5
films is 37.30 ± 2.60 and 31.73 ± 0.55 nm, respectively. Using the maximum emission wavelength and average roughness, it was verified that the SRO
5
film present silicon nanoparticles with a larger size than the SRO
10
film. Finally, atomic force microscopy reveals the presence of some peaks on the surface of SRO films. The density of these peaks increases after the last etching step in both films. This could indicate the formation of Si-nanopyramid structures at the SRO/Si-substrate interface. Our results show that the surface oxidation plays an important role in the PL quenching.