Direct evidence for strain inhomogeneity in inxGa1-xN epilayers by raman spectroscopy

M.R. Correia, S.M.D.S. Pereira, E.M. Ferreira Pereira Lopes, J. Frandon, I.M. Watson, C. Liu, E. Alves, A.D. Sequeira, N. Franco

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

This contribution is focused on Raman analysis of the InxGa1-xN alloy. It presents direct evidence that both strain and composition effects must be taken into account to interpret the Raman experimental results. Raman studies have been commonly discussed in view of composition inhomogeneity only, neglecting the possible existence of strain depth variations, recently shown to occur for layers grown above the critical layer thickness. The effects of this variation on the A1(LO) phonon frequency could only be investigated by combining both structural and Raman measurements. In this letter, a set of InxGa1-xN layers has been chemically etched during different periods, allowing the depth variation of the phonon frequency to be unambiguously evidenced. Comparing the Raman spectra before and after etching, two distinct InxGa1-xN regions, differing on their strain state, are identified: a relaxed one, found near the surface region; another one, grown coherently (i.e., pseudomorphic) to the GaN buffer layer. These results are in excellent agreement with an additional reciprocal space map analysis.
Original languageEnglish
Pages (from-to)2235-2237
Number of pages3
JournalApplied Physics Letters
Volume85
Issue number12
DOIs
Publication statusPublished - 2004

Keywords

  • inxGa1-xN epilayers
  • raman spectroscopy
  • surface cleaning
  • crystal structures

Cite this