Formation of Ge quantum dots on Si substrate using consecutive deposition of Ge/C and in situ post annealing

Shinji Hatakeyama, Yuhki Itoh, Tomoyuki Kawashima, Katsuyoshi Washio

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Effects of intermediate carbon between amorphous Ge and Si surface on formation of Ge dots recrystallized through post-annealing were studied. The samples were prepared by solid-source molecular beam epitaxy system with electron beam gun for C sublimation and K-cell for Ge evaporation. C and Ge were deposited sequentially at 200 °C and Ge/C/Si was subsequently annealed in MBE chamber. Ge dots were formed at annealing temperature (TA) of 400 °C for Ge(1 nm)/C(0.25 ML)/Si. The dot size increased with TA, and both Ge(2 2 0) peak intensity measured by in-plane XRD and dot density were the highest at TA of 700 °C. A strong correlation between dot density and surface roughness indicated recrystallization of Ge occurred during the dot formation promoted by Si-C bonds. Concerning the effect of C coverage, there was an optimum at 0.25 ML which gave good crystallinity of Ge dots. Coalesced dots with bad crystallinity were observed for less or more C coverage. This was considered that dot formation combined with S-K growth mode due to large bare Si surface occurred at small C coverage and excess C incorporated into Ge dots at large C coverage. In terms of Ge thickness, there was also an optimum at 1 nm to provide sufficient Ge atoms without excess.

Original languageEnglish
Pages (from-to)28-32
Number of pages5
JournalMicroelectronic Engineering
Volume125
DOIs
Publication statusPublished - 2014 Aug 1

Keywords

  • Carbon
  • Ge
  • Molecular beam epitaxy (MBE)
  • Quantum dot
  • Si

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Surfaces, Coatings and Films
  • Electrical and Electronic Engineering

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