Effects Of Deposition Conditions On The Conductivity And Photoconductivity Of rf Sputtered a-Ge:H and a-Gel_xCx:H

J. Shinar; H.-S. Wu

doi:10.1117/12.949919

6 March 1989 Effects Of Deposition Conditions On The Conductivity And Photoconductivity Of rf Sputtered a-Ge:H and a-Ge_{1_x}C_x:H

J. Shinar, H.-S. Wu

Author Affiliations +

Proceedings Volume 1016, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion VII; (1989) https://doi.org/10.1117/12.949919
Event: 1988 International Congress on Optical Science and Engineering, 1988, Hamburg, Germany

Abstract

a-Ge:H and a-Ge_{1_x}C_x:H films were prepared by rf sputtering of 4 polycrystalline Ge target in a background vacuum ~4x10^-7 at rf power 5O<P<600W (0.27-3.3W/cm²), target-to-substrate distances 1≤d≤7", varying partial pressures of Ar, H2, and propane, and flow rates f. The dark conductivity σ_d and photoconductivity σ_ph increase with increasing d up to 6", apparently due to thermalization of the ions and Ge atoms bombarding the growing film. σ_d and σ_ph also increase at f<lsccm, due to the incorporation of oxygen and other impurities from the background residual atmosphere. At the optimal values of f and d, σ_ph and ad increase with P. Although all increases in aph are significant relative to those bf previously reported rf sputtered a-Ge:H, the values arb still much lower than those of glow discharge deposited films, which are in turn lower than those of rf magnetron sputtered films grown in high vacuum (<5x10^-9 torr). The similar behavior of σd and σ_ph, the relatively long lifetimes of the carriers ι - 0.8ms but very low mobility μ 5x10^-7 cm4/Vsec and low subgap absorption suggest that the transport is dominated by defects near the mobility edge. The failure of a biased screen placed above the substrate to affect σ_ph suggests that the high values of aph reported using rf magnetron sputtering are at least in part due to the improved background vacuum. Although incorporation of significant amounts of carbon sharply reduces σ_ph, a small content, sufficient to increase the optical gap to 1.3-1.4eV, has little effect on σph.

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J. Shinar and H.-S. Wu "Effects Of Deposition Conditions On The Conductivity And Photoconductivity Of rf Sputtered a-Ge:H and a-Ge_{1_x}C_x:H", Proc. SPIE 1016, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion VII, (6 March 1989); https://doi.org/10.1117/12.949919

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KEYWORDS

Sputter deposition

Argon

Chemical species

Solar energy

Plasma

Germanium

Ions

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