Effect of Boron Doping on Structural, Optical, and Electrical properties of Hydrogenated Nanocrystalline Silicon Thin Films Grown by the Catalytic Chemical Vapour Deposition (Cat-CVD) Method
Abstract
In this paper, we report the synthesis of highly conducting boron-doped p-type hydrogenated nanocrystalline Silicon (nc-Si:H) films by the catalytic chemical vapour deposition (Cat-CVD) method using the mixture of silane (SiH4) and diborane (B2H6) without hydrogen (H2) dilution. Variation in the properties of the film with B2H6 gas flow rate was studied and revealed that the boron doping induces amorphization in nc-Si:H film structure. Upon doping, the Fourier transform infrared spectroscopy (FTIR) spectroscopy analysis shows the shift of hydrogen bonding from Si-H2 to Si-H configuration. The hydrogen content was found < 3 at.% while the bandgap remains as high as 1.6 eV or more over the entire range of the B2H6 gas flow rate studied. At optimized B2H6 gas flow rate, we have obtained p-type nc-Si:H films having a high bandgap (1.9 eV), high dark conductivity (3.36 S/cm) with low hydrogen content (2.3 at.%) with a reasonably high deposition rate (26.2 Å/s). The obtained films can be useful as a window layer in a-Si:H based p-i-n and tandem solar cells.