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Nano-structured GeySi1-y:H Films Deposited by Low Frequency Plasma for Photovoltaic Application

Published online by Cambridge University Press:  15 March 2011

Andrey Kosarev
Affiliation:
Electronics, Institute National for Astrophysics, Optics and Electronics, Puebla, 72840, Mexico
Alfonso Torres
Affiliation:
Electronics, Institute National for Astrophysics, Optics and Electronics, Puebla, 72840, Mexico
Carlos Zuniga
Affiliation:
Electronics, Institute National for Astrophysics, Optics and Electronics, Puebla, 72840, Mexico
Marco Adamo
Affiliation:
“Lambda Energia”, S.A. de C.V., Cuernavaca, Morelos, 62160, Mexico
Liborio Sanchez
Affiliation:
Electronics, Institute National for Astrophysics, Optics and Electronics, Puebla, 72840, Mexico
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Abstract

In this work we present the study of fabrication, Ge incorporation, structure and electronic properties of nano-structured GeySi1-y:H films with y>0.5 prepared by low frequency (LF) PECVD. GeySi1-y:H films were deposited by LF PECVD at a frequency f= 110 kHz from SiH4+GeH4+H2 gas mixture. SiH4 and GeH4 flows were varied to fabricate the films in wide range of 0<y<l. Hydrogen dilution was varied in the range of RH =20 to 80. Structure of the films was studied by AFM and SEM with consequent image processing to extract statistical parameters such as grain distribution and mean values. Composition of the films was characterized by SIMS and EDX. Electronic properties were characterized by temperature dependence of conductivity, spectral dependence of optical absorption. Sub-gap absorption was characterized by Urbach energy, EU; and defect absorption, αD. We observed grain like nano-structure with Gauss distribution of grain diameters by both AFM and SEM measurements. The most interesting films had mean grain diameter<D> = 24.0±0.7 nm, dispersion D=11.0±0.2 nm and fill factor FF=0.313, Ge content y=0.96-0.97(by SIMS and EDS). These films showed also the lowest values of Urbach energy EU = 0.030 eV and low defect absorption αD = 5×102 cm −1 (at photon energy hv = 1.04 eV) indicating on low density of localized states in mobility gap. Doped films have been also fabricated and studied. Finally we shall discuss application of the above films in photovoltaic devices.

Type
Research Article
Copyright
Copyright © Materials Research Society 2009

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References

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