Hydrogenated Nano-Crystalline Silicon Thin Films in SiO_2 Matrix for Next Generation Solar Cells Using Glow Discharged Decomposition

摘要

Hydrogenated Nanocrystalline Silicon (nc-Si:H) thin films using SiH_4/H_2 mixture by glow discharged decomposition were investigated on c-Si and glass substrates. The effects of substrate temperature on the Structural, Optical and Electrical properties of the films were investigated by X-ray diffraction, Raman scattering, FT/IR, Optical transmission and Atomic Force Microscopy (AFM). Substrate temperatures ([Tsb]) of the films were changed from 100℃ to 250℃. It has been revealed the strong dependence on the film's properties with the substrate temperatures. XRD and Raman measurements were shown that the higher substrate temperature (250℃) exhibits the highest crystalline volume fraction ([p] = 95%) and the lowest crystalline size ([Ω] = 3.5 nm) as well, having the highest H-content and the lowest 0-content. At 250℃, the lowest mobility and the highest resistivity were also found to be ～37.5 cm~2/v.s and 7.35 Ω-cm. Refractive index and the optical energy gap (E_g) were estimated by 3.8 and 1.9 eV having the growth rate of 4.2 nm/min. At 250℃, it was resulted in a blue shift of the absorption edge having uniform grain distributions. Results indicate that in situ hydrogen cleaning effects is prominent and localized orderly high density Si-Si bonds are exhibiting quantum size effects at highest substrate temperature.