Marc Herbert Brodsky

Glow discharge preparation of amorphous hydrogenated silicon from higher silanes

Amorphous hydrogenated silicon has been deposited by plasma decomposition of Si2H6 and Si3H8. A major feature of the process is a deposition rate enhancement of over a factor of 20 compared to monosilane. The resulting films are compositionally similar to monosilane‐produced intrinsic a‐Si(H), but films deposited at 300 °C substrate temperature show greater photoconductivity. On the basis of our deposition experiments and the known thermolysis chemistry of the silanes, a conjectural model for the deposition process is presented.

Deposition and doping of a‐Si:H from Si2H6 plasmas

Compared to SiH4, the plasma deposition of amorphous hydrogenated silicon from Si2H6 results in compositionally similar films, deposited at rates at least an order of magnitude higher. The films also display larger dark and photoconductivties, a result related directly to higher Ef in the intrinsic Si2H6‐prepared material. The effect is structural, not impurity‐dominated. Dopant incorporation is also found to be strongly influenced by the silicon source, as is the doping efficiency. For a given gas phase concentration of n‐type dopant (PH3), the distribution coefficient is Ceff<1 for Si2H6 plasmas, compared to Ceff≳1 for depositions from SiH4, yet film electrical properties are comparable. On the p‐type side, much smaller differences are observed with B2H6 doping of the two sources. Finally, a‐Si:H plasma deposition chemistry is examined within the context of a neutral radical model and hydrogen etching experiments.