Characterization of Si-rich a-Si N :H alloys deposited by 1yx x laser-CVD

Highly silicon-rich amorphous hydrogenated silicon nitride a-Si1yxNx:H.alloys 0.11-x-0.34. were prepared by ArF laser-induced photolysis performed in parallel configuration using Ar-buffered disilanerammonia gas mixtures. The combined UV-induced photodissociation of both precursor gases generates high growth rates in the range of 0.3 to 0.7 nm sy1 whose dependencies on the substrate temperature 200–4008C.and the percentage of disilane in the gas mixture are presented. While the growth rate increases exponentially with the temperature, its variation with the decreasing disilane content shows an initial decrease followed by sharp increase at a critical precursor gas composition and subsequent decrease for gas mixtures having very low disilane content. Films have been analysed by Fourier transform infrared spectroscopy FTIR., energy dispersive spectroscopy EDS., profilometry and UV spectroscopy. The band gap measurements reveal that these silicon-rich films with compositions below the percolation threshold of Si–Si bonds i.e., x-0.52.show fine band gap controllability in the range of 1.6 to 2.9 eV. The band gap value seems to be directly linked to the bonded hydrogen content and to have low sensitivity to variations in the nitrogen content. q1999 Elsevier Science B.V. All rights reserved