On the Growth of Thin-Film AlGaN/GaN Epitaxial Heterostructures on Hybrid Substrates Containing Layers of Silicon Carbide and Porous Silicon

Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid...     

Laser-Printed Plasmonic Metasurface Supporting Bound States in the Continuum Enhances and Shapes Infrared Spontaneous Emission of Coupled HgTe Quantum Dots

In order to advance the development of quantum emitter-based devices, it is essential to enhance light-matter interactions through coupling between semiconductor quantum dots with high quality factor resonators. Here, efficient tuning of the emission properties of HgTe quantum dots in the infrared spectral region is demonstrated by coupling them to a plasmonic metasurface that supports bound states in the continuum. The plasmonic metasurface, composed of an array of gold nanobumps, is fabricated using single-step direct laser printing, opening up new opportunities for creating exclusive 3D plasmonic nanostructures and advanced photonic devices in the infrared region. A 12-fold enhancement of the photoluminescence in the 900–1700 nm range is observed under optimal coupling conditions. By tuning the geometry of the plasmonic arrays, controllable shaping of the emission spectra is achieved, selectively enhancing specific wavelength ranges across the emission spectrum. The observed enhancement and shaping of the emission are attributed to the Purcell effect, as corroborated by systematic measurements of radiative lifetimes and optical simulations based on the numerical solution of Maxwell's equations. Moreover, coupling of the HgTe photoluminescence to high quality factor modes of the metasurface improves emission directivity, concentrating output within an ≈20° angle.     

Engineering of a Biomimetic Interface between a Native Dental Tissue and Restorative Composite and Its Study Using Synchrotron FTIR Microscopic Mapping

The aim of this work is to develop a biomimetic interface between the natural tooth tissue and the restorative composite and to study it on the basis of synchrotron micro-FTIR mapping and multidimensional processing of the spectral data array. Using hierarchical cluster analysis of 3D FTIR data revealed marked improvements in the formation of the dentine/adhesive/dental hybrid interface using a biomimetic approach. The use of a biomimetic strategy (application of an amino acid–modified primer, alkaline calcium and a nano-c-HAp–modified adhesive) allowed the formation of a matrix that can be structurally integrated with natural dentine and dental composite. The biomimetic hybrid layer was characterised by homogeneous chemical composition and a higher degree of conversion of the adhesive during polymerisation, which should provide optimal integration of the dental composite with the dentine.     

Effect of silicon on relaxation of the crystal lattice in MOCVD–hydride Al<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ga<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>As:Si/GaAs(100) heterostructures

The X-ray diffraction and infrared spectroscopy data for MOCVD-hydride Al _x Ga_{1 − x} As:Si/GaAs(100) heterostructures and homoepitaxial GaAs:Si/GaAs(100) structures doped with Si to a content of up to ∼1 at % are reported. It is shown that, in the homoepitaxial heterostructures, the formation of alloys with Si yields a decrease in the crystal lattice parameters of the epitaxial layer and a negative lattice mismatch with the single-crystal substrate (Δa < 0). At the same time, the formation of quaternary alloys in the Al _x Ga_{1 − x} As:Si/GaAs(100) heterostructures is not accompanied by any pronounced strains in the crystal lattice. By introducing Si into the epitaxial layers of these heterostructures, it is possible to attain complete matching of crystal lattice parameters of the film and substrate in the appropriately chosen technological conditions of growth of the epitaxial layers.     

Specific features of the sol-gel formation and optical properties of 3d metal/porous silicon composites

The composition and optical properties of composite materials based on porous silicon with iron, cobalt, and nickel deposited by the sol-gel technique are studied. It is shown that the deposition of metal-oxide films onto the surface of porous silicon enables stabilization of the photoluminescence and an increase in its intensity, as well as the storage of hydrogen in the porous layer.     

Structure and optical properties of heterostructures based on MOCVD (Al x Ga1 − x As1 − y P y )1 − z Si z alloys

Epitaxial heterostructures produced by MOCVD on the basis of Al _x Ga_{1 ? x} As ternary alloys with the composition parameter x ≈ 0.20–0.50 and doped to a high Si and P atomic content are studied. Using the high-resolution X-ray diffraction technique, scanning electron microscopy, X-ray microanalysis, Raman spectroscopy, and photoluminescence spectroscopy, it is shown that the epitaxial films grown by MOCVD are formed of five-component (Al _x Ga_{1 ? x} As_{1 ? y} P _y )_{1 ? z} Si _z alloys.     

Infrared reflectance spectra and morphologic features of the surface of epitaxial AlxGa1−x As/GaAs(100) heterostructures with the ordered AlGaAs2 phase

The infrared reflectance spectra associated with lattice vibrations in the epitaxial Al_xGa_1?x As/GaAs(100) heterostructures with different Al content in the cation sublattice are studied. The structures are grown by metal-organic chemical vapor deposition. In the spectrum of the structure with x ≈ 0.50, the vibration modes corresponding to the superstructurally ordered AlGaAs₂ phase are detected. The atomic force microscopy of the surface of the sample with x ≈ 0.50 reveals areas of ordered nano-scaled profile, with a period of ～ 115 nm. The ordered domains involve the AlGaAs₂ structured phase.     

Vegard’s law and superstructural phases in Al<Subscript>x</Subscript>Ga<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>As/GaAs(100) epitaxial heterostructures

The lattice constants of Al_xGa_1?x As epitaxial alloys with various AlAs (x) contents are determined for AlxGa_1?xAs/GaAs(100) heterostructures grown by MOC-hydride epitaxy using X-ray diffractometry and an X-ray back-reflection method. An ordered AlGaAs₂ (superstructural) phase is found in epitaxial heterostructures with x ≈ 0.50. The lattice constant of this phase is smaller than the lattice constants of an Al_0.50Ga_0.50As alloy and GaAs single-crystal substrate.