Published online by Cambridge University Press: 01 February 2011
Nanocrystalline germanium thin-films deposited on glass by plasma-enhanced chemical vapor deposition from germane and hydrogen were doped with phosphorus and boron. We report some electrical transport and structural properties of Ge films as a function of dopant species and doping levels. The dark conductivities of the phosphorus- and boron-doped films are approximately three to four orders of magnitude higher than the intrinsic nanocrystalline germanium. In the solid phase, phosphorus comprised about 1 atomic percent in the Ge bulk over the range of source gas ratios used, and the conductivity remained fairly constant, indicating saturated conditions. Boron comprised about 10 atomic percent in Ge at the highest dark conductivity, while increased doping turned the films amorphous. To test the doped layers for device applications, an all-nanocrystalline germanium p-i-n diode was constructed and showed rectification when measured in the dark at room temperature.