Growth of undoped ZnO films with improved electrical properties by radical source molecular beam epitaxy

Ken Nakahara, Tetsuhiro Tanabe, Hidemi Takasu, Paul Fons, Kakuya Iwata, Akimasa Yamada, Koji Matsubara, Ralf Hunger, Shigeru Niki

Research output: Contribution to journalArticle

83 Citations (Scopus)

Abstract

High-quality undoped ZnO epitaxial films with mobilities as high as 120cm2V-1s-1 and carrier concentrations as low as 7.6 × 1016 cm-3 have been grown on (112̄0) a-sapphire substrates using low-temperature buffer layers, a slow substrate cooling process and a modified oxygen radical cell. Pole figure measurements reveal that a-plane sapphire substrates are effective for the elimination of 30° rotation domains, which usually appear in the case of ZnO growth on c-sapphire. The low-temperature buffer layers allow high-temperature growth, because initial ZnO growth does not occur with high initial growth temperature. The use of slow substrate cooling prevents the deterioration of the electrical properties of the ZnO films. Use of quartz insulators in the oxygen radical cell eliminates aluminum contamination, which is a serious problem when using conventional alumina insulators.

Original languageEnglish
Pages (from-to)250-254
Number of pages5
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Volume40
Issue number1
DOIs
Publication statusPublished - 2001 Jan
Externally publishedYes

Keywords

  • a-plane sapphire
  • Buffer layer
  • Electrical property
  • RS-MBE
  • ZnO

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)

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