3-Dimensional Self-Ordered Multilayered Ge Nanodots on SiGe

Abstract

Three-dimensional (3D) self-ordered Ge nanodots in cyclic epitaxial growth of Ge/SiGe superlattice on Si0.4Ge0.6 virtual substrate (VS) were fabricated by reduced pressure chemical vapor deposition. By the Ge/SiGe superlattice deposition, dot-on-dot alignment and <100> alignment were obtained toward the vertical and lateral direction, respectively. Facets and growth mechanism of Ge nanodots and key factors of alignment were studied. Two types of Ge nanodots were observed, diamond-like nanodots composed of {105} and dome-like nanodots composed of {113} and {159} facets. The Ge nanodots tend to grow directly above the nanodots of the previous period as these regions show a relative higher tensile strain induced by the buried nanodots. Thus, this dot-on-dot alignment is sensitive to the SiGe spacer thickness, and it degrades when the SiGe spacer is over 82 nm. The Ge content of the SiGe spacer ranging 45-52% affects the lateral alignment and the size uniformity of Ge nanodots because of the strain balance between the superlattice and the VS. When the strain is balanced, 3D aligned Ge nanodots can be achieved.

Vertical alignment control of self-ordered multilayered Ge nanodots on SiGe

“…The template was fabricated by 20 cyclic depositions of 52 nm Si 0.48 Ge 0.52 and 12.5 nm Ge SL on Si 0.4 Ge 0.6 VS at 550 °C. 22) On the template, a layer of 45-63 nm SiGe with Ge content of 45%-52% was deposited at 550 °C or 500 °C without air exposure.…”

“…For the Ge nanodot formation, we have reported dot-on-dot vertically and laterally aligned multilayered Ge nanodots with a Si spacer on SiGe nanodot SL as a template 21) and with a SiGe spacer on a SiGe virtual substrate (VS) without pre-structuring. 22) In this study, we fabricated 3D self-ordered multilayered Ge nanodots on a SiGe VS with SiGe spacers. We also studied the influence of SiGe spacer growth conditions on the surface morphology and on Ge nanodot formation on these surfaces, which is the key to the vertical alignment control.…”

Heteroepitaxy of group IV materials for future device application

“…In this case, the driving force of the SiGe nanodot formation is a local tensile strain of Si on the buried SiGe nanodot. 33,34) In the case of 3D-ordered Ge nanodot formation by Ge/ SiGe SL, key parameters for vertical and staggered alignment are also non-uniform local strain and surface roughness of the SiGe spacer. 35,36) By depositing the SiGe spacer at 550 °C, vertical alignment of Ge nanodot is obtained because of smooth SiGe spacer surface formation.…”

“…We summarized a method for abrupt SiGe quantum well (QW) fabrication by C-delta doping, 29) the influence of strain on the surface reaction of heteroepitaxial SiGe growth, 30) and three-dimensional (3D) aligned SiGe and Ge nanodot fabrication by proactively managing strain and surface energies. [31][32][33][34][35][36]…”