Characteristics of a-si:h films prepared by ecr cvd as a function of the h 2/sih 4

Abstract

The optical, electrical and structural properties of hydrogenated amorphous silicon films were investigated as a function of the H 2/SiH 4 ratio. The films were deposited by electron cyclotron resonance plasma chemical vapor deposition method in the source gas limited and electron flux limited mode. In the source gas limited mode, the properties of amorphous silicon films were improved with increasing deposition rate photoconductivity, hydrogen content increased and optical band gap, full width at half maximum of the Raman spectroscopy and the ratio of the concentration of dihydride to that of monohydride decreased. In the electron flux limited mode, the optical, electrical and structural properties as well as the deposition rate did not improved any more. The photoconductivity was over 10 −5 Ω −1 cm −1 when the optical band gap was 1.75 ~ 1.77 eV, FWHM was below 75 cm −1, hydrogen content was about 21 at.% and the ratio of dihydride to the monohydride was about 1.5 in the electron flux limited mode.