3-Dimensional Self-Ordered Multilayered Ge Nanodots on SiGe

• Published in: ECS transactions 2022-09, Vol.109 (4), p.343-350
• Main Authors: Wen, Wei-Chen, Schubert, Markus Andreas, Zöllner, Marvin Hartwig, Tillack, Bernd, Yamamoto, Yuji
• Format: Article
• Language: English
• ISSN: 1938-5862; 1938-6737
• DOI: 10.1149/10904.0343ecst

Three-dimensional (3D) self-ordered Ge nanodots in cyclic epitaxial growth of Ge/SiGe superlattice on Si 0.4 Ge 0.6 virtual substrate (VS) were fabricated by reduced pressure chemical vapor deposition. By the Ge/SiGe superlattice deposition, dot-on-dot alignment and 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.