In situ correlation between the optical and electrical properties of thin intrinsic and n-type microcrystalline silicon films

Abstract

Intrinsic and n-type microcrystalline silicon thin films were deposited on intrinsic hydrogenated amorphous silicon by the layer-by-layer technique. The growth of the samples has been analyzed in situ by kinetic ellipsometry, spectroscopic ellipsometry, and dark conductivity measurements. This in situ analysis has shown that the process of deposition can be divided into four phases: incubation, nucleation, growth, and steady state. Moreover we have found striking differences between the growth of undoped and n-type samples in both the kinetics of the formation of crystallites and the zone where the nucleation of crystallites takes place. According to our in situ conductivity measurements, the percolation threshold occurs for a crystalline volume fraction higher than 20% in both cases. Moreover, we can produce very thin (6 nm) and highly conductive (σd≈0.2 S cm−1) n-type microcrystalline silicon films on intrinsic amorphous silicon.