Growth of Tetragonal Si via Plasma-Enhanced Epitaxy

We have been able to synthesize directly the tetragonal Si by low temperature plasma-enhanced chemical vapor deposition using hydrogen and silane as the precursor and carrier gas, respectively. With the optimization of growth conditions, a stable tetragonal epitaxial Si can be grown on a crystalline Si substrate at large scale. By combining X-ray diffraction and high resolution transmission electron microscopy measurements, we found that the epitaxial layer has smaller in-plane but larger out-of-plane lattice parameters as compared to the crystalline substrate. The existence of hydrogen platelets in epitaxy is also observed, which affects the diffraction patterns along that direction. We attribute the formation of tetragonal Si to the hydrogenated-cluster-assisted epitaxy. Other possible reasons including host sites of hydrogen atoms and thermal expansion coefficients are also discussed

Growth of Vertical GaAs Nanowires on an Amorphous Substrate via a Fiber-Textured Si Platform

We demonstrate the vertical self-catalyzed molecular beam epitaxy (MBE) growth of GaAs nanowires on an amorphous SiO₂ substrate by using a smooth [111] fiber-textured silicon thin film with very large grains, fabricated by aluminum-induced crystallization. This generic platform paves the way to the use of inexpensive substrates for the fabrication of dense ensembles of vertically standing nanowires (NWs) with promising perspectives for the integration of NWs in devices

Morphology Tailoring and Growth Mechanism of Indium-Rich InGaN/GaN Axial Nanowire Heterostructures by Plasma-Assisted Molecular Beam Epitaxy

We investigate the growth mechanism of axially heterostructured InGaN/GaN nanowires (NWs) as a function of the flux conditions. The InGaN heterostructure morphology critically depends on the In/Ga flux ratio affecting the local V/III ratio at the NW growth front. Locally N-rich conditions are associated with tapered island-like morphologies, while metal-rich conditions, leading to the formation of a stable Indium adsorbed layer at the NW growth front, promote the growth of heterostructures with a disk-like shape. Based on experimental results and theoretical predictions, we demonstrate that this indium ad-layer acts as a surfactant inducing a modification of the InGaN heterostructure growth mode. The impact of flux conditions and strain relaxation on the Indium incorporation are also addressed. The resulting insertions present abrupt interfaces and a homogeneous In distribution for In contents up to 40%