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Microsrtuctures and Electrical Characterization of CVD-W and Mo Films as Contacts in Photocells

Published online by Cambridge University Press:  15 February 2011

Kostadinka A. Gesheva ,
G. I. Stoyanov ,
R. Stefanov  and
E. S. Vlakhov
Kostadinka A. Gesheva
Affiliation:
Central Laboratory of Solar Energy and New Energy Sources at Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd,1784 Sofia, Bulgaria
G. I. Stoyanov
Affiliation:
Central Laboratory of Solar Energy and New Energy Sources at Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd,1784 Sofia, Bulgaria
R. Stefanov
Affiliation:
Central Laboratory of Solar Energy and New Energy Sources at Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd,1784 Sofia, Bulgaria
E. S. Vlakhov
Affiliation:
Institute of Solid State Physics at Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd, 1784 Sofia, Bulgaria
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Abstract

Tungsten and molybdenum hexacarbonyls were used as precursors in chemical vapour deposition process for preparation of W and Mo thin films. Pyrolitical decomposition of these precursors proceeds at temperatures of 250–400°C. Thin films with thicknesses in the range of 0,02–1 μm were deposited on different substrates - bare or covered with CdTe glass, and monocrystalline Si. Microstructural studies performed by Reflection High Energy Electron Diffraction (RHEED) method showed that films deposited tend to grow textured. This is discussed as probably due to differences in the growth rate for various crystal planes. The sheet resistances of the as-deposited W and Mo films are in the range of 20–30 Ω/□ for thicknesses of 0.15 μm. After thermal annealing the resistance of W films drops to about 2 Ω/□ and for Mo films to about 9Ω/□. Decreasing in the resistivity of the films is tightly connected with the decreasing in the impurities concentration. These impurities are considered to be in the base of the observed behaviour of the temperature dependence of the electrical resistance of the films. The CVD-W and Mo films are studied as back contacts on CdTe layer in CdS/CdTe photocells. In the paper some preliminary results are presented for the sheet and contact resistances when CVD W and Mo films are deposited at lower temperatures on the surface of CdTe layers, deposited by closespaced sublimation method. The thin film materials, produced by CVD technology look promising with respect to the required high deposition rates and extremely wide deposition areas in the mass production of solar cells.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 363 , 1994 , 119
Copyright
Copyright © Materials Research Society 1995

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