Tailoring Strain and Morphology of Core–Shell SiGe Nanowires by Low-Temperature Ge Condensation

Abstract

Selective oxidation of the silicon element of silicon germanium (SiGe) alloys during thermal oxidation is a very important and technologically relevant mechanism used to fabricate a variety of microelectronic devices. We develop here a simple integrative approach involving vapor-liquid-solid (VLS) growth followed by selective oxidation steps to the construction of core-shell nanowires and higher-level ordered systems with scalable configurations. We examine the selective oxidation/condensation process under nonequilibrium conditions that gives rise to spontaneous formation of core-shell structures by germanium condensation. We contrast this strategy that uses reaction-diffusion-segregation mechanisms to produce coherently strained structures with highly configurable geometry and abrupt interfaces with growth-based processes which lead to low strained systems with nonuniform composition, three-dimensional morphology, and broad core-shell interface. We specially focus on SiGe core-shell nanowires and demonstrate that they can have up to 70% Ge-rich shell and 2% homogeneous strain with core diameter as small as 14 nm. Key elements of the building process associated with this approach are identified with regard to existing theoretical models. Moreover, starting from results of ab initio calculations, we discuss the electronic structure of these novel nanostructures as well as their wide potential for advanced device applications.

Raman microscopy and infrared optical properties of SiGe Mie resonators formed on SiO2 via Ge condensation and solid state dewetting

“…4. The Ge content appeared to be close to the expected one from the fabrication process [25][26][27][28] . The compressive strain in all three SiGe layers is quite strong up to ∼-0.027 for the partially condensed layer 3).…”

“…One set of UT-SGOI substrates was obtained by following a well-established procedure [25][26][27][28] . In Fig.…”

Si and SiGe Nanowire for Micro-Thermoelectric Generator: A Review of the Current State of the Art

“…Particularly, κ of the C-S NWs at 388 K is 1.1-2.5 W m −1 K −1 , remarkably reduced from the Ge NWs (2.3-3.9 W m −1 K −1 ). Some theoretical works have applied first-principle calculations and Boltzmann transport theory to model the TE performance of Ge/Si or Si/Ge core-shell NWs (Wingert et al, 2011;Yang et al, 2015;David et al, 2017). In a study (Chen et al, 2010), with the optimal carrier concentration of 2.64 × 10 25 m −3 , the achieved maximum ZT value reached 0.85 at 300 K in Ge/Si C-S NWs with P-type doping, significantly larger than 0.36 in pure Si NWs.…”

Quantum Confined Stark Effect on the Linear and Nonlinear Optical Properties of SiGe/Si Semi Oblate and Prolate Quantum Dots Grown in Si Wetting Layer

“…They are considered the most realistic models that are close to the experimental samples. The semiconducting material Si 1−η Ge η , (where η is the concentration of Ge) has been used for many electronic devices due to its large density, high dielectric constant and excellent optical properties [49][50][51][52][53]. Their nonlinear optical properties like AC, RIC, second harmonic generation (SHG) and third harmonic generation (THG) provide a thorough insight into the mechanism of the optical response.…”