Influence of double buffer layers on properties of Ga-polarity GaN films grown by rf-plasma assisted molecular-beam epitaxy

C. F. Zhu, J. Q. Xie, W. K. Fong, C. Surya

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Ga-polarity GaN thin films were grown on sapphire (0001) substrates by rf-plasma assisted molecular beam epitaxy (MBE) using a double buffer layer, which consisted of an intermediate-temperature GaN buffer layer (ITBL) grown at 690 °C and a conventional AlN buffer layer deposited at 740 °C. Raman scattering spectra showed that the E2 (high) mode of GaN film grown on conventional AlN buffer layer is at about 570 cm-1, and shifts to 568 cm-1 when an ITBL was used. This indicates that the ITBL leads to the relaxation of residual strain in GaN film caused by mismatches in the lattice constants and coefficients of thermal expansion between the GaN epilayer and the sapphire substrate. Compared to the GaN film grown on the conventional AlN buffer layer, the GaN film grown on an ITBL shows higher Hall mobility and substantial reduction in the flicker noise levels with a Hooge parameter of 3.87 × 10-4, which is believed to be, to date, the lowest reported for GaN material. These results imply that the quality of Ga-polarity GaN films grown by MBE can be significantly improved by using an ITBL in addition to the conventional low-temperature AlN buffer layer.

Original languageEnglish
Pages (from-to)2413-2416
Number of pages4
JournalMaterials Letters
Volume57
Issue number16-17
DOIs
Publication statusPublished - May 1 2003
Externally publishedYes

Keywords

  • Electrical properties
  • Epitaxial growth
  • GaN thin films
  • Molecular beam epitaxy
  • Raman scattering

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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