ALTERNATIVE DOPING OF P-TYPE AMORPHOUS-SILICON FILMS USING BORON-TRIFLUORIDE

P-type amorphous hydrogenated silicon thin films have been prepared using plasma-enhanced chemical vapour deposition with boron trifluoride instead of diborane as the dopant gas. The influence of the substrate temperature (T(s)), the radio frequency (r.f.) power density (RFP) and the dopant gas concentration (C(BF3)) have been investigated. The applicability of boron trifluoride to make device-quality p-type amorphous silicon has been demonstrated. The incorporation of fluorine to the lattice has been deduced from the analysis of the infrared transmission spectra. The experimental results show interesting features such as the inhibition of bandgap degradation in a wide doping range, which has been associated with the presence of fluorine. P-type thin films with 1.82 eV optical gap, 4.8 X 10(-4) (OMEGA cm)-1 conductivity and 0.43 eV activation energy, have been produced.