Properties of fluorinated glow-discharge amorphous silicon

Abstract

Amorphous silicon films were prepared by plasma decomposition of SiF4.+SiF2 gas. Structural analysis, electronic-transport-property measurements, optical-property measurements, and electronspin-resonance measurements were performed as a function of deposition and annealing temperature. Hydrogenated amorphous silicon (a-Si:H) samples were prepared in a separate identical reactor under similar plasma conditions for reference. The results indicate that compensation of dangling bonds by fluorine alone can be obtained, yielding ESR values of the order of 10' spins/cm . The a-Si:F films can be doped. The dark conductivity of a-Si:F increases with spin density, but the photoconductivity is low and independent of the spin density. The differences between a-Si;F and a-Si:H are interpreted in terms of the different diffusivity and bond strength of fluorine and hydrogen in the a-Si matrix. These differences result in a larger density of tail states in a-Si:F relative to a-Si:H samples of equal spin densities.

Optoelectronic properties of fluorine-doped silicon nitride thin films

“…From Lorentz-Lorenz model [14], one can presumably expect the structural and composition changes of oxide film. In view of structure and composition, the decrease of refractive index with halogen addition can be attributed to the fact that the polarization characteristics of Si-N network in the Si-rich SiN x films would be changed from tetrahedral sp 3 to more planar sp 2 orbital, which is less polarizable [15]. It is due to the breakage of Si-N network structure by etching effect of the atomic fluorine.…”

Effects of Fluorine Implantation into Hydrogenated Amorphous Silicon

“…It is also shown that there is tremendous decrease of more than three orders of magnitude with CF in the ratio of phototo dark conductivity, _ph/GDA. It has been reported in the literature that compared to a-Si:H the photoconductivity of a-Si:F is lower by about four orders of magnitude, and the low photoconductivity in a-Si:F has been attributed to wider band tail and larger density of band tail states as a consequence of the lack of the ability of fluorine atoms to relieve strained Si-Si bonds [6]. Our results are consistent with this view and suggest that higher fluorine concentration leads to higher density of tail states and therefore lower photoconductivity.…”

“…Since then, the study of fluorinated amorphous silicon alloys has received considerable attention for its stability against heating and light illumination ' [2][3][4][5][6]. There are also quite a number of studies on the properties of fluorine implanted amorphous silicon [7][8][9][10][11][12][13].…”

N and p-type doping of PECVD a-SiC:H obtained under “silane starving plasma” condition with and without hydrogen dilution

“…The higher electrical conductivity of BF 2 + implanted sample can also be related to the fluorine presence in the film. In fact, in a-Si:H literature [21,22], the incorporation of fluorine atoms has been found to have effects similar to those of hydrogen in reducing the density of states in the bandgap. Matsumura et al [23] have reported the p-type doping of a-Si:F achieved by the addition of BF 3 in the sputtering gas, without incorporating hydrogen.…”