Effect of Deposition Conditions and Crystallinity of Substrate on Phase Transition of Hydrogenated Si Films

Abstract

Hydrogenated intrinsic Si (Si:H) thin films were deposited by a plasma-enhanced chemical vapor deposition technique, and the effect of the SiH4 flow rate ([SiH4]) and hydrogen dilution ratio (R) on the crystalline phase transition was studied using Raman spectroscopy and high-resolution transmission electron microscopy. The crystalline volume fraction (X c) was strongly affected by [SiH4] as well as R, and higher X c could be achieved by using a lower [SiH4] at the same R. The dependence of phase transition on the crystallinity of the under-lying layer was also investigated by depositing Si:H films on various substrates. To evaluate the effects of [SiH4] and R on the quality of amorphous-Si:H (a-Si:H) films, etch rates and absorption coefficients were obtained by an H2-plasma etching process and UV-Vis spectrophotometry, respectively. Even under the deposition condition resulting in a-Si:H films, the deposition rate decreased by a factor of 3 to 4.6, and the film density considerably increased as R increased from 4 to 19. On the other hand, the absorption coefficient very slightly decreased with R. The presence of microcrystalline Si:H could be observed only from the samples deposited with R>19 when the film was deposited on amorphous substrate.

Highly improved passivation of c-Si surfaces using a gradient i a-Si:H layer

“…Typically, Si peaks are observed from 350 to 550 cm À1 , and peaks associated specifically with a-Si and c-Si are positioned near 480 cm À1 and 510 cm À1 , respectively. 21 The prephase nucleation of nc-Si leads to a minor red-shift of the a-Si peak at 480 cm À1 in the Raman spectra. 22,23 As shown in Fig.…”

Amorphous SiGe:H Thin Film Solar Cells with Light Absorbing Layers of Graded Bandgap Profile

“…Note that a chamber cleaning process using F-containing gas was not carried out between deposition steps for each layer. According to the Raman spectroscopic analysis, the p-Si:H and n-Si:H layers were mixed phases of microcrystalline and amorphous phases, 16 and all i-SiGe:H and i-Si:H layers were amorphous. The samples were constructed to have the same cell structure except the a-SiGe:H light absorbing layer.…”