Nonstoichiometric composition shift in physical vapor deposition of CdTe thin films

Ken K. Chin, Zimeng Cheng, Alan E. Delahoy

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

While it is being debated whether Cd vacancy is an effective p-dopant in CdTe, and whether CdTe thin film in solar energy application should be Cd-deficient or Cd-rich, in the theory of CdTe physical vapor deposition (PVD) it has been assumed that both the source material and the thin film product is stoichiometric. To remediate the lack of effective theory, a new PVD model for CdTe photovoltaic (PV) modules is presented in this work, in which the composition of the CdTe thin film under growth is a parameter determined by the source CdTe composition as well as the growth condition. The solid phase Cd1-δTe1+δ compound under deposition temperature is treated as a solid solution with a mole of excess pure Te or Cd as solute and one mole of congruently grown CdTe as solvent. Assuming that the vapor pressure of Te2 can be calculated by using the law of solid solution PTe=H0+aH1+a2H2 round the congruent composition, where the molar number a and the constants H0, H1 and H2 as functions of temperature T are extracted from the experimental data. Thus, the mole fraction of solute in the grown CdTe thin film as well as the growth rate, as a function of the solute mole fraction in the source CdTe can be determined.

Original languageEnglish (US)
Pages (from-to)32-37
Number of pages6
JournalJournal of Crystal Growth
Volume418
DOIs
StatePublished - May 15 2015

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Inorganic Chemistry
  • Materials Chemistry

Keywords

  • A1. Growth models
  • A3. Physical vapor deposition processes
  • B1. Cadmium compounds
  • B2. Semiconducting II-VI materials

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