GaAs/Ge crystals grown on Si substrates patterned down to the micron scale

Abstract

Monolithic integration of III-V compounds into high density Si integrated circuits is a key technological challenge for the next generation of optoelectronic devices. In this work, we report on the metal organic vapor phase epitaxy growth of strain-free GaAs crystals on Si substrates patterned down to the micron scale. The differences in thermal expansion coefficient and lattice parameter are adapted by a 2-lm-thick intermediate Ge layer grown by low-energy plasma enhanced chemical vapor deposition. The GaAs crystals evolve during growth towards a pyramidal shape, with lateral facets composed of {111} planes and an apex formed by {137} and (001) surfaces. The influence of the anisotropic GaAs growth kinetics on the final morphology is highlighted by means of scanning and transmission electron microscopy measurements. The effect of the Si pattern geometry, substrate orientation, and crystal aspect ratio on the GaAs structural properties was investigated by means of high resolution X-ray diffraction. The thermal strain relaxation process of GaAs crystals with different aspect ratio is discussed within the framework of linear elasticity theory by Finite Element Method simulations based on realistic geometries extracted from cross-sectional scanning electron microscopy images. V

Dislocation-Free SiGe/Si Heterostructures

“…Let us now analyze the possibility to grow other materials. In Figure 5, the final morphology of SiC [24] (panel a), GaN [25] (panel b), GaAs [26,27] (panel c), and GaAs/Ge [28,29] (panel d) crystals grown on Si pillars is displayed. The various deposition techniques are listed in the caption.…”

Lattice tilt and strain mapped by X-ray scanning nanodiffraction in compositionally graded SiGe/Si microcrystals

“…The out-of-equilibrium method of growth, low-energy plasmaenhanced chemical vapour deposition (LEPECVD) (Rosenblad et al, 1998), results in a dense network of micrometresized three-dimensional epitaxial crystals. The use of deeply patterned substrates, along with growth by LEPECVD, initially demonstrated for the growth of Ge on Si(001) (Falub et al, 2013;Isa, Pezzoli et al, 2015;Rozbořil et al, 2016), was further extended to other materials and growth techniques, such as GaAs growth by metal-organic vapour phase epitaxy (Bietti et al, 2013;Falub et al, 2014;Taboada et al, 2014Taboada et al, , 2016, GaN growth by plasma-assisted molecular beam epitaxy (Isa, Chè ze et al, 2015) and SiC growth by chemical vapour deposition Meduň a, Kreiliger et al, 2016). The basic principle behind the approach is that dislocations are confined close to the heterointerface, while the bulk of the crystal remains dislocation free (Marzegalli et al, 2013;Falub et al, 2013;Isa et al, 2013).…”

Lattice bending in three-dimensional Ge microcrystals studied by X-ray nanodiffraction and modelling

“…It involves the fast epitaxial growth of the mismatched material onto an Si substrate patterned at the micrometre scale into a regular array of high aspect ratio pillars, resulting in a dense network of micrometre-sized threedimensional epitaxial crystals. The approach was initially demonstrated for the growth of Ge on Si(001) (Falub et al, 2012), and afterwards it was extended to other material combinations and crystallographic orientations (Bergamaschini et al, 2013;Falub et al, 2014;Taboada et al, 2014Taboada et al, , 2016Isa, Chè ze et al, 2015;Isa et al, 2016). The dislocations formed in these epitaxial structures are confined near the interface with the substrate, whereas the bulk of the crystal remains defect free (Marzegalli et al, 2013;Falub et al, 2013;Isa, Pezzoli et al, 2015;Rozbořil et al, 2016).…”