Diffusion length measurements of microcrystalline silicon thin films prepared by hot-wire/catalytic chemical vapor deposition (HWCVD)

Abstract

Hydrogenated microcrystalline silicon (μc-Si:H) films prepared by using the hot-wire/catalytic chemical vapor deposition (HWCVD) technique at low substrate temperatures between 185 °C and 220 °C with different silane concentrations (SC) were investigated using steady-state photocarrier grating (SSPG) and the steady-state photoconductivity methods (SSPC). Crystalline volume fractions ( I C RS) obtained from Raman spectroscopy change from 0.22 to 0.77. The diffusion length ( L D) is measured at generation rates between G = 10 19 and 10 21 cm − 3 s − 1. L D changes from 27 nm to 270 nm, with maximum values around SC = 5%. The dependence of L D on SC is similar to that observed for similar quality microcrystalline silicon films prepared using the VHF-PECVD technique. The grating quality factor, γ 0, drops from about 0.9 to 0.5 after transition to the microcrystalline regime as indication of scattering from surface patterns.