a-Si:H films: Influence of P- and B-doping on infra-red absorption bands

The infra-red spectra of P- and B-doped hydrogenated amorphous silicon films grown by means of an evaporation method have been measured. The SiHn stretching and wagging (or rocking) absorption bands have been examined by varying the dopant content measured by Auger analysis. On increasing the doping, a reduction of hydrogen content has been noticed with an enhancing of zeroth-order moment of Si-H stretching at the expense of the Si-H2 one. Analogous results for B-doped films have been observed. Since no frequency shift towards higher frequencies of the stretching bands has been measured, the observed changes of the intensity of the bands have been attributed to structure modifications rather than to variations in the electronegativity in the neighbours of the silicon atom. In particular, the monohidride configuration with an overall decrease in the number of defects seems to be favoured by the deposition technique adopted.