DEPOSITION OF PHOSPHORUS DOPED MICROCRYSTALLINE SILICON BELOW 70-DEGREES-C AT 70 MHZ

Microcrystalline silicon doped with phosphorus has been prepared with Very High Frequency Glow Discharge at low power and low deposition temperatures. The transition from amorphous to microcrystalline growth depends critically on the dilution of silane in hydrogen such, that a decrease in the substrate temperature can be compensated by a stronger dilution of silane in hydrogen to still achieve microcrystalline growth. Upon annealing up to 200-degrees-C the conductivities increase considerably for as-deposited material, both amorphous and microcrystalline. Whereas this is not accompanied by changes in the Raman spectra, there are changes in the optical absorption spectra upon annealing: as-grown microcrystalline material shows a strong increase of the subgap absorption that is attributed to an increase in the free carrier absorption due to de-passivation of dopants in the crystallites; as-grown amorphous material shows a small reduction of the subgap absorption due to annealing of defects.