Doping of amorphous and microcrystalline silicon films deposited at low substrate temperatures by hot-wire chemical vapor deposition

The gas phase doping of amorphous (a-Si:H) and microcrystalline $(μc-Si:H)$ silicon thin films deposited at substrate temperatures of 25 °C and 100 °C by hot-wire chemical vapor deposition is studied. Phosphine was used for n-type doping and diborane for p-type doping. The electronic and structural properties of the doped films are studied as functions of hydrogen dilution. Films were deposited on glass and polyethylene terephthalate. Similar dark conductivities, $σd,$ were obtained for the doped films deposited on either substrate. $σd$ above $10−6$ Ω⁻¹ cm⁻¹ were obtained for a-Si:H films doped n-type at 25 °C and 100 °C $(σd>10−4 Ω−1 cm−1)$ and for a-Si:H doped p-type only at 100 °C. $σd,$ equal or above $10−1$ $Ω−1 cm−1,$ were obtained for $μc-Si:H$ doped p-type at 25 °C and 100 °C for $μc-Si:H$ doped n-type only at 100 °C. Isochronal annealing at temperatures up to 200 °C reveals that, while the dopants are fully activated in microcrystalline samples, they are only partially activated in amorphous films deposited at a low substrate temperature.