Defect free strain relaxation of microcrystals on mesoporous patterned silicon

TL;DR

This paper presents a novel silicon substrate patterning technique enabling defect-free epitaxial growth of lattice-mismatched materials like germanium, by exploiting elastic deformation and strain attenuation in microcrystals.

Contribution

The study introduces a deep patterning and electrochemical porosification method for silicon that achieves defect-free, strain-relaxed epitaxial growth of Ge on Si.

Findings

Full elastic relaxation of Ge microcrystals demonstrated

Dislocation-free heteroepitaxy achieved

Porous micropillars facilitate strain management

Abstract

A perfectly compliant substrate would allow the monolithic integration of high-quality semiconductor materials such as Ge and III-V on Silicon (Si) substrate, enabling novel functionalities on the well-established low-cost Si technology platform. Here, we demonstrate a compliant Si substrate allowing defect-free epitaxial growth of lattice mismatched materials. The method is based on the deep patterning of the Si substrate to form micrometer-scale pillars and subsequent electrochemical porosification. The investigation of the epitaxial Ge crystalline quality by X-ray diffraction, transmission electron microscopy and etch-pits counting demonstrates the full elastic relaxation of defect-free microcrystals. The achievement of dislocation free heteroepitaxy relies on the interplay between elastic deformation of the porous micropillars, set under stress by the lattice mismatch between Ge and Si, and on the diffusion of Ge into the mesoporous patterned substrate attenuating the mismatch strain at the Ge/Si interface.