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Title: A one-dimensional Fickian model to predict the Ga depth profiles in three-stage Cu(In,Ga)Se{sub 2}

We present a one-dimensional Fickian model that predicts the formation of a double Ga gradient during the fabrication of Cu(In,Ga)Se{sub 2} thin films by three-stage thermal co-evaporation. The model is based on chemical reaction equations, structural data, and effective Ga diffusivities. In the model, the Cu(In,Ga)Se{sub 2} surface is depleted from Ga during the deposition of Cu-Se in the second deposition stage, leading to an accumulation of Ga near the back contact. During the third deposition stage, where In-Ga-Se is deposited at the surface, the atomic fluxes within the growing layer are inverted. This results in the formation of a double Ga gradient within the Cu(In,Ga)Se{sub 2} layer and reproduces experimentally observed Ga distributions. The final shape of the Ga depth profile strongly depends on the temperatures, times and deposition rates used. The model is used to evaluate possible paths to flatten the marked Ga depth profile that is obtained when depositing at low substrate temperatures. We conclude that inserting Ga during the second deposition stage is an effective way to achieve this.
Authors:
 [1] ;  [2] ;  [3] ;  [1]
  1. International Iberian Nanotechnology Laboratory, Avenida Mestre Jose Veiga s/n, 4715-330 Braga (Portugal)
  2. (Germany)
  3. Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin (Germany)
Publication Date:
OSTI Identifier:
22304286
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 20; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CHEMICAL REACTIONS; COMPUTERIZED SIMULATION; COPPER COMPOUNDS; DEPOSITION; DISTRIBUTION; EVAPORATION; FABRICATION; FICK LAWS; GALLIUM ADDITIONS; GALLIUM COMPOUNDS; INDIUM COMPOUNDS; LAYERS; ONE-DIMENSIONAL CALCULATIONS; SELENIUM COMPOUNDS; SPATIAL DISTRIBUTION; SUBSTRATES; SURFACES; THIN FILMS