Microcrystalline silicon carbide alloys prepared with HWCVD as highly transparent and conductive window layers for thin film solar cells

New insight into the microstructure and doping of unintentionally n-type microcrystalline silicon carbide

“…In order to minimize a possible impact of the film thickness we adjusted the deposition time to obtain a thickness of approximately 200 nm for all samples in the study. The influence of F MMS on the material properties is comparable with the influence of an increase of hydrogen dilution, as reported by Finger et al 2 and Miyajima et al 6 They conclude that an increase of hydrogen dilution leads to a decrease of disorder in the microstructure. Similarly, we derived from the FWHM of the FTIR and XRD data that the reduction of F MMS leads to a decrease of disorder in the microstructure.…”

“…To date, it is known that dark conductivity increases with higher crystalline volume fraction. 2,6 However, K€ ohler et al 12 showed that the material is either crystalline or amorphous. Therefore, it is still unclear, how the structural properties of lc-SiC:H are related to the electrical properties.…”

“…In the literature, O and N impurities originating from contamination are discussed as possible candidates for the creation of donor-like states within the energy gap of lcSiC:H. 2,6,7 From c-SiC it is well known that N is a very good shallow donor impurity, due to its low ionization energy. 28 Unlike the case of unintentionally n-type doped microcrystalline silicon, where the use of gas purifiers during deposition decreased [O] and r d , 29 Finger et al 2 reported that the electrical properties of unintentionally n-type doped lcSiC:H were not affected by gas purifiers. In the present work, although r d covers a very large range-9 orders of magnitude- [O] In the following we discuss two plausible options that might explain the strong increase of r d , which is dominated by an increase of n, without any increase of the donor impurity concentrations.…”

“…Probably a major reason is that all electrical transport properties, i.e., r d , n, and l, are measured in plane to the growth direction whereas L SiC , derived from XRD, represents the average coherent domain size perpendicular to the growth direction. From literature it is known that HWCVD SiC grains grow in the form of columns along the film growth, 2,12,27 whereas PECVD SiC grains grow in the form of well-distributed ellipsoids. 34 …”

Preparations of P‐ and N‐doped hydrogenated microcrystalline cubic silicon carbide films by VHF plasma enhanced chemical vapor deposition method for Si thin film solar cells

“…From these results, it can be concluded that n-type μc-3C-SiC:H films were successively prepared by VHF PECVD method. Note that the dark conductivity of the non-doped film has been scattered between 10 -8 S/cm to 10 -5 S/cm even if employing almost the same deposition conditions (see also [9]). Thus, only the upper value (about 10 -5 S/cm) is plotted in Fig.…”