Metastable (GaSb)(1-x)(Sn2)x alloys: Crystal growth and phase stability of single crystal and polycrystalline layers

L. Romano*, J. E. Sundgren, S. A. Barnett, J. E. Greene

*Corresponding author for this work

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Single-phase metastable (GaSb)(1-x)(Sn2)x alloys with x ≤ 0.23 far exceeding the equilibrium solid solubility limit of x {less-than or approximate} 0.02 for Sn in GaSb, have been grown by rf sputter deposition. The key feature allowing the growth of single phase alloys was the use of low energy ion-bombardment-induced collisional mixing during deposition. Films grown at elevated temperatures Ts on GaAs(100) substrates were found to be single crystals while polycrystalline films with very strong (220) perferred orientation and grain sizes of 20-40 nm were obtained on amorphous glass substrates. The maximum film growth temperatures Tm at which single phase films could be obtained was a function of the negative substrate potential Vs during deposition and the composition x. For Vs = 75 V, Tm ranged from 375 °C at x = 0.06 to 125 °C at x = 0.23. Crystal growth and post-annealing studies both indicated that the transformation from the single-phase metastable state to the equilibrium (GaSb + βSn) state occurs through a continuous set of metastable GaSb-rich phases and that Sn precipitates out first in the α-diamond structure and then transforms to the β-tetragonal structure. In single crystal films, the GaSb-rich phase precipitates out coherently with the alloy matrix. The activation energy for phase separation ranged from ∼ 1.4 eV for alloys with x = 0.06 to 0.9 eV at x = 0.23. A phase map for crystal growth, plotted as a function of Ts and x, and an annealing transformation diagram for (GaSb)0.86(Sn2)0.14 was determined.

Original languageEnglish (US)
Pages (from-to)233-241
Number of pages9
JournalSuperlattices and Microstructures
Volume2
Issue number3
DOIs
StatePublished - 1986

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Electrical and Electronic Engineering

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