Growth, structure, and transport properties of thin (>10 nm) n-type microcrystalline silicon prepared on silicon oxide and its application to single-electron transistor

Microcrystalline silicon (μc-Si:H) thin films were prepared at 300 °C on glass. Their structure and transport properties were studied in a wide range of film thickness ranging from 10 nm to 1 μm. The crystal fraction increases monotonously from ∼64% to ∼100% as film thickness increases. Electron mobility first increases with increasing film thickness at thicknesses smaller than 50 nm but saturates at larger thickness. This mobility behavior is explained by percolation transport through crystalline grains. These results are different from those obtained with preferentially oriented polycrystalline silicon films. It is related to the difference in the microstructure evolution in which subsequent film growth is influenced by the growth surface structure. A single-electron transistor fabricated in 30-nm-thick μc-Si:H exhibits Coulomb blockade effects at 4.2 K. This result indicates that amorphous phases which exist between crystalline grains behave as tunnel barrier for electrons.