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Title: A kinetic model for the metallorganic chemical vapor deposition of CdTe

Abstract

The industrial application of cadmium telluride (CdTe) semiconducting layers is still limited by the large amount of defects contained in the films and by the problem of the reproducible control of the level and type of conductivity. Overcoming these difficulties requires a better understanding of the physical and chemical phenomena underlying the deposition process. In particular, in order to improve the quality of the films and to optimize the deposition processes, it is of great importance to understand the elementary kinetic mechanism governing the growth of CdTe. Epitaxial deposition of cadmium telluride through metallorganic chemical vapor deposition was investigated. A detailed elementary kinetic scheme of surface and gas-phase reactions occurring during the deposition process was developed and embedded in a one-dimensional fluid-dynamic model based on the boundary-layer theory. Kinetic constants of gas-phase reactions were either found in the literature or determined through quantum chemistry methods. The most important surface processes were identified and studied through quantum chemistry. Quantum chemistry calculations were performed through the three-parameter Becke-Lee-Yang-Parr hybrid (B3LYP) density functional theory using the 3-21G** basis set. Bond dissociation energies of adsorbed methyl groups were calculated, and according to these data, it was proposed that the growth process proceeds through themore » adsorption of dimethylcadmium, which successively loses a methyl group to give the adsorbed methylcadmium species. Adsorbed methylcadmium successively reacts with a dimethyltellurium gas-phase molecule to give ethane and methylcadmium telluride, which after the loss of the methyl group becomes part of the film. The effect of the carrier gas on the deposition chemistry was also investigated and a possible reason for the decrease in growth rate observed when the carrier gas is changed from hydrogen to helium was proposed. The productivity of the model was demonstrated through the simulation of experimental growth rate and gas-phase composition data reported in the literature.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Politecnico di Milano (IT)
OSTI Identifier:
20003177
Resource Type:
Journal Article
Journal Name:
Journal of the Electrochemical Society
Additional Journal Information:
Journal Volume: 146; Journal Issue: 9; Other Information: PBD: Sep 1999
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; MATHEMATICAL MODELS; CADMIUM TELLURIDES; CHEMICAL VAPOR DEPOSITION; CADMIUM TELLURIDE SOLAR CELLS; FABRICATION

Citation Formats

Cavallotti, C., Bertani, V., Masi, M., and Carra, S. A kinetic model for the metallorganic chemical vapor deposition of CdTe. United States: N. p., 1999. Web. doi:10.1149/1.1392467.
Cavallotti, C., Bertani, V., Masi, M., & Carra, S. A kinetic model for the metallorganic chemical vapor deposition of CdTe. United States. doi:10.1149/1.1392467.
Cavallotti, C., Bertani, V., Masi, M., and Carra, S. Wed . "A kinetic model for the metallorganic chemical vapor deposition of CdTe". United States. doi:10.1149/1.1392467.
@article{osti_20003177,
title = {A kinetic model for the metallorganic chemical vapor deposition of CdTe},
author = {Cavallotti, C. and Bertani, V. and Masi, M. and Carra, S.},
abstractNote = {The industrial application of cadmium telluride (CdTe) semiconducting layers is still limited by the large amount of defects contained in the films and by the problem of the reproducible control of the level and type of conductivity. Overcoming these difficulties requires a better understanding of the physical and chemical phenomena underlying the deposition process. In particular, in order to improve the quality of the films and to optimize the deposition processes, it is of great importance to understand the elementary kinetic mechanism governing the growth of CdTe. Epitaxial deposition of cadmium telluride through metallorganic chemical vapor deposition was investigated. A detailed elementary kinetic scheme of surface and gas-phase reactions occurring during the deposition process was developed and embedded in a one-dimensional fluid-dynamic model based on the boundary-layer theory. Kinetic constants of gas-phase reactions were either found in the literature or determined through quantum chemistry methods. The most important surface processes were identified and studied through quantum chemistry. Quantum chemistry calculations were performed through the three-parameter Becke-Lee-Yang-Parr hybrid (B3LYP) density functional theory using the 3-21G** basis set. Bond dissociation energies of adsorbed methyl groups were calculated, and according to these data, it was proposed that the growth process proceeds through the adsorption of dimethylcadmium, which successively loses a methyl group to give the adsorbed methylcadmium species. Adsorbed methylcadmium successively reacts with a dimethyltellurium gas-phase molecule to give ethane and methylcadmium telluride, which after the loss of the methyl group becomes part of the film. The effect of the carrier gas on the deposition chemistry was also investigated and a possible reason for the decrease in growth rate observed when the carrier gas is changed from hydrogen to helium was proposed. The productivity of the model was demonstrated through the simulation of experimental growth rate and gas-phase composition data reported in the literature.},
doi = {10.1149/1.1392467},
journal = {Journal of the Electrochemical Society},
number = 9,
volume = 146,
place = {United States},
year = {1999},
month = {9}
}