Electronic properties of microcrystalline SiGe-thin films by Hall-experiments and photo- and dark-transport

Transport properties of microcrystalline Si1−xGex thin films (0⩽x⩽0.56) deposited in a VHFPE-CVD process from disilane–germane mixtures under strong H2 dilution have been analyzed by dark conductivity, photoconductivity, and by Hall-experiments. Mobilities of electrons and holes at room temperature amount to μnRT=1 cm2 V−1 s−1, and μpRT=0.25 cm2 V−1 s−1 and (μτ)n- and (μτ)p-products decrease by increasing Ge-content from 10−7 m2 V−1 by a factor of 30, and from 4×10−10 cm2 V−1 by a factor of 2, respectively. We see a transition from n-type to p-type conduction at x≈0.56. Within the temperature regime of traditional operation of opto-electronic devices (2⩽103/T⩽4) electron and hole transport is dominated by low mobility states such as tail states or by grain boundary barriers.