ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The optical, electronic and structural properties of thin films deposited by Hot-wire chemical vapor deposition with filament temperatures, Tfil, between 1500 and 1900 °C from silane and hydrogen are studied. The substrate temperature, Tsub, was kept constant at 220 °C. Amorphous silicon films (a-Si:H) are obtained at high filament temperatures, low deposition pressures and low hydrogen-to-silane flow rate ratio (Tfil∼1900 °C, p〈30 mTorr and FH2/FSiH4≤1). At these deposition conditions, high growth rates are observed (rd≥10 A(ring)s−1) both with and without hydrogen dilution, and no silicon deposition was observed on the filaments. However, if a lower filament temperature is used (Tfil∼1500 °C) a transition from a-Si:H to microcrystalline silicon (μc-Si:H) occurs as the pressure is decreased from above 0.3 Torr to below 0.1 Torr. The highest dark conductivity and lowest activation energy, of ∼1 Scm−1 and 〈0.1 eV, respectively, were observed for μc-Si:H deposited at p∼50 mTorr. In this Tfil regime, μc-Si:H growth is achieved without hydrogen dilution, for substrate temperatures as low as ∼150 °C, and for very thin films (∼0.05 μm). Silicon growth on the filaments is observed. For both Tfil regimes, an amorphous to microcrystalline transition is also observed when the hydrogen dilution is increased (FH2/FSiH4(approximately-greater-than)4). A kinetic growth model is developed, which suggests that the transition from amorphous to microcrystalline can be explained by considering a balance between the concentration of atomic hydrogen and the concentration of the precursor to silicon deposition (SixHz with z≤3x) near the sample. This concentration ratio is shown to be controlled both by the deposition pressure, p, and the filament temperature, Tfil. © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.362501
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