We report on an effective way to obtain high electron mobility (∼103cm2∕Vs) in lowly doped hydrogenated nanocrystalline silicon (nc-Si:H) thin films by constructing nc-Si:H∕crystalline Si (c-Si) heterostructures. The enhancement has been demonstrated in a comparative study on nc-Si:H thin films grown on p- and n-type c-Si, as well as insulating glass substrates through temperature- and magnetic-field-dependent Hall-effect measurements. The effect has been attributed to the ordered structure and narrow boundaries between the nanograins, with the help of microstructure pictures from high-resolution transmission electron microscopy. In addition to the detailed individual transport information of carriers in the nc-Si:H systems, we observe clear evidence for the formation of a two-dimensional electron gas at the nc-Si:H∕c-Si interfaces. These results are discussed within the framework of the Boltzmann theory and the quantum interference theory.

No abstract