Accommodation of SiGe strain on a universally compliant porous silicon substrate

International audienceThe growth of heteroepitaxial planar fully strained SiGe layers with high Ge concentration and large thickness enables tailoring electronic properties for enhanced transport properties and photoemission. We give here the first experimental and theoretical proof that high temperature flashed porous silicon layers (HT-PSi) perfectly accommodate the stress of SiGe layers and provide compliant substrates with unprecedented capabilities for the fabrication of planar SiGe nanomembranes. We show that the stress driven morphological evolution leading to self-organized quantum dots commonly observed on nominal Si (001) is fully inhibited when growing SiGe on such a HT-PSi substrate. The elastic behavior of HT-PSi results from two specific features: It is ten times softer than Si and tensily strained. Theoretical analysis proves that the compliant behavior of HT-PSi is due to the strain effect, while on the contrary its elastic softness favors the development of 3D growth. The inhibition due to the tensile strain produces atomically flat layers free of misfit dislocation