Defect free strain relaxation of microcrystals on mesoporous patterned silicon

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.

Large‐Scale Formation of Uniform Porous Ge Nanostructures with Tunable Physical Properties

“…This enables the distinction between the critical angle of PGe layer (θ PGe ) and of the bulk Ge (θ Ge ) as shown in Figure 4b. The porosity can therefore be calculated using Equation (1). Variation of PGe critical angle with porosity is shown in Figure S2, Supporting Information.…”

“…The XRR was used to measure the critical angle of PGe layer. The porosity (P) was then calculated using Equation (1) where θ PGe and θ Ge correspond to the critical angle of the PGe layer and of the bulk Ge, respectively. [52,53] (1 ) 100…”

“…Porous semiconductor materials have received an increasing interest for both fundamental research and advanced applications owing to their unique mechanical and physicochemical properties compared to their bulk material counterparts. [ 1–4 ] Porous germanium (PGe) in particular shows a potential in wide range of implementations such as energy storage systems, [ 5–10 ] thermoelectric devices, [ 11 ] sensors, [ 12–14 ] optoelectronics, [ 15,16 ] or synthesis of nanocomposite materials. [ 17–19 ] Moreover, PGe has recently been demonstrated as an efficient virtual substrate for epitaxial growth of detachable Ge membranes [ 20 ] and III‐V heterostructures with high crystalline quality [ 21,22 ] paving the way to direct application in the development of lightweight and flexible photovoltaics and optoelectronics.…”

“…Porous semiconductor materials have received an increasing interest for both fundamental research and advanced applications owing to their unique mechanical and physicochemical properties compared to their bulk material counterparts. [1][2][3][4] Porous germanium (PGe) in particular shows and low-cost technique providing PGe layers with high material purity and densely packed nanocrystals. However, its widespread adoption remains strongly dependent on the controllable production of homo geneous PGe layer on large surfaces.…”

Self‐Rolled‐Up Ultrathin Single‐Crystalline Silicon Nanomembranes for On‐Chip Tubular Polarization Photodetectors

“…[30][31][32] Typically, the epitaxial interface between Si and Ge can induce ≈4.18% interfacial strain. [33][34][35] When the epitaxial single-crystalline Si nanomembrane on Ge or Si 1−x Ge x sacrificial layer is released, residual stress at the epitaxial interface can spontaneously drive the formation of 3D structures, including tubular and wrinkled structures, [7,36,37] which is a solid foundation for the preparation of 3D Si nanomembranes electronic and optoelectronic devices.…”