New strategies for producing defect free SiGe strained nanolayers

Abstract

Strain engineering is seen as a cost-effective way to improve the properties of electronic devices. However, this technique is limited by the development of the Asarro Tiller Grinfeld growth instability and nucleation of dislocations. Two strain engineering processes have been developed, fabrication of stretchable nanomembranes by deposition of SiGe on a sacrificial compliant substrate and use of lateral stressors to strain SiGe on Silicon On Insulator. Here, we investigate the influence of substrate softness and pre-strain on growth instability and nucleation of dislocations. We show that while a soft pseudo-substrate could significantly enhance the growth rate of the instability in specific conditions, no effet is seen for SiGe heteroepitaxy, because of the normalized thickness of the layers. Such results were obtained for substrates up to 10 times softer than bulk silicon. The theoretical predictions are supported by experimental results obtained first on moderately soft Silicon On Insulator and second on highly soft porous silicon. On the contrary, the use of a tensily pre-strained substrate is far more efficient to inhibit both the development of the instability and the nucleation of misfit dislocations. Such inhibitions are nicely observed during the heteroepitaxy of SiGe on pre-strained porous silicon.

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.…”

When finite-size effects dictate the growth dynamics on strained freestanding nanomembranes

“…The chemical potential m is the sum of the elastic energy density on the surface E and of the capillary term gk, where g is the surface energy (we neglect here the surface energy anisotropy 38 ) and k ¼ À(h xx + h yy ) is the surface local mean curvature. Given the solution (13), one nds that a modulation of wave-vector k evolves in the linear approximation as h 1 (k, t) ¼ e ik$r+st with sðk; e; hÞ ¼ A k ðe; HÞk 3 À k 4 ;…”

“…In this case, the surface is not characterized by a unique wave-vector, but may be decomposed as the sum of different Fourier modes with equal amplitude at t ¼ 0 (describing a white noise). We consider only the linear regime of the surface diffusion equation (that is relevant in the smallslope approximation) where elasticity is given at rst order in h by eqn (13). Hence, the different Fourier modes evolve independently following eqn (15), starting with equal amplitude, and evolving with different growth rates.…”

“…Different techniques are available for the production of crystalline NM on different kinds of support. [9][10][11][12][13] The resulting NM can be deformed and are attractive for exible optoelectronics, photonics and nanoelectronics, e.g. in radiofrequency or thermally degradable devices, magnetotransport systems, micromechanical systems, infrared phototransistors and also for biological applications.…”