Richard Michael Plecenik

Kinetics and mechanism of amorphous hydrogenated silicon growth by homogeneous chemical vapor deposition

A new method of amorphous hydrogenated silicon (a‐Si:H) chemical vapor deposition is presented in which SiH4 is homogeneously decomposed at high temperature and pressure to produce films on low‐temperature substrates having up to 30‐at. % H and properties very similar to plasma‐deposited material. Kinetic studies provide a film growth activation energy of 54 kcal/mole, confirming that SiH2 is the primary gas phase intermediate. A mechanism based on SiH2 chemistry is presented to account for the rapid surface reactions leading to a‐Si:H growth and its possible relevance to the plasma deposition process is emphasized.

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.

Low defect density amorphous hydrogenated silicon prepared by homogeneous chemical vapor deposition

Compositional, structural and transport data are presented for amorphous hydrogenated silicon (a‐Si:H) prepared by homogeneous chemical vapor deposition (HOMOCVD). We find a remarkable similarity in properties between HOMOCVD and plasma a‐Si:H, including a nearly identical range (250–300 °C) for the preparation of highly photoconductive films. However, unlike plasma material, HOMOCVD a‐Si:H exhibits negligible photo‐induced instabilities (Staebler–Wronski effect) and low spin concentrations over a wide span of deposition conditions. These results indicate that a significant defect‐creating reaction, most likely surface Si‐H bond scission, is occurring in the plasma environment, but absent in HOMOCVD.

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.