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Fast near-IR (NIR) emitters are highly valuable in telecommunications and biological imaging. The most established NIR emitters are epitaxially grown In[sub.x]Ga[sub.1−x]As quantum dots (QDs), but epitaxial growth has several disadvantages. Colloidal synthesis is a viable alternative that produces a few NIR-emitting materials, but they suffer from long photoluminescence (PL) times. These long PL times are intrinsic in some NIR materials (PbS, PbSe) but are attributed to emission from bright trapped carrier states in others. We show that Cd[sub.3]P[sub.2] QDs possess substantial trap emission with radiative times >10[sup.1] ns. Surface passivation through shell growth or coordination of Lewis acids is shown to accelerate the NIR emission from Cd[sub.3]P[sub.2] QDs by decreasing the amount of trap emission. This finding brings us one step closer to the application of colloidally synthesized QDs as quantum emitters.

Experiments on the growth of self-assembled InP/GaInP.sub.2 quantum dots in dielectric mask 0.1-1 m apertures by MOVPE epitaxy have been carried out. A sequence of operations for the implementation of the lift-off lithography method is proposed and implemented. The possibility of obtaining apertures with 100 nm diameter and less is shown. Combination of thermally deposited SiO.sub.2 and wet etching is shown to produce minimal amount of nonradiative defects and results in a stable PL signal from single QDs in the aperture.

The paper presents the results of studying the dark currents of nB(SL)n structures with a superlattice (SL) in the barrier region based on Hg.sub.1 - xCd.sub.xTe grown by molecular beam epitaxy (MBE) in a wide range of experimental conditions. Dark currents were measured in the temperature range from 11 to 300 K for mesa structures with different cross-sectional diameters. The temperature dependences of the bulk component of the dark current density and the surface leakage current density are determined. It is shown that in the studied structures the current-voltage characteristics (CVCs) are formed by both the bulk and surface components of the current depending on the temperature and bias voltage.

For ABO.sub.3 perovskites, the magnetic and electronic properties couple strongly to the BO.sub.6 octahedral rotations and distortions. Therefore, precise control of the octahedral rotations and distortions via epitaxial strain and interfacial octahedral connectivity has become the key for engineering novel functionalities in ABO.sub.3 heterostructures and superlattices. In this paper, we investigated the local octahedral rotations in a [(1 unit cell (u.c.)//4 u.c.) x 13] LaNiO.sub.3/LaGaO.sub.3 superlattice grown on a (001) SrTiO.sub.3 substrate. By using aberration-corrected high-resolution transmission electron microscopy, we found that the octahedral rotations of NiO.sub.6 adopted the same [100] and [010] rotational magnitudes as the neighboring GaO.sub.6 till the surface of the superlattice. Our results indicate that in LaNiO.sub.3-based superlattices, the NiO.sub.6 rotations can be precisely controlled via interfacial octahedral connectivity when the thickness of the LaNiO.sub.3 layer is only 1 unit cell.

High-quality VO.sub.2 films with precisely controlled thicknesses were grown on sapphire substrates by plasma-assisted oxide molecular beam epitaxy (MBE). To evaluate the degradation of semiconductor-metal transition (SMT) behavior of VO.sub.2 films under solar radiation, the temperature-driven SMT was investigated by measuring the electrical resistance during heating and cooling processes under solar simulator AM1.5, which provided illumination approximately matching the natural sunlight. The distinct reversible SMTs were observed for all the samples, whereas a remarkably conflicting trend in resistance change for extremely thin and thick samples was observed after exposure to the sunlight soaking system. The corresponding mechanism was proposed based on sunlight-induced resistance changes due to the transformation in the electron correlation and structural symmetry. The results might be especially attractive for some specific applications of VO.sub.2 films where solar radiation was inevitable.

Sn-doped β-Ga.sub.2O.sub.3 epitaxial layers have been grown on (100) β-Ga.sub.2O.sub.3 substrates by metal organic vapour-phase epitaxy. Triethylgallium (TEGa), molecular oxygen (O.sub.2) and tetraethyltin (TESn) were used as Ga, O and Sn precursors, respectively. Layers grown at optimized temperature and chamber pressure, i.e. 850 °C and 5 mbar, had flat surfaces with a rms roughness of about 600 pm. Structural analysis by transmission electron microscopy revealed that the main defects in the layers were stacking faults and twin lamella. The incoherent boundaries of these defects are supposed to act as compensation and scattering centres, limiting the carrier mobility. Sn was homogeneously incorporated with a flat profile throughout the whole layer at concentration levels ranging from 2 x 10.sup.17 to 3 x 10.sup.19 cm.sup.-3 proportionally to the used TESn flux. All layers were electrically conductive. However, an unambiguous Hall effect was measurable only for Sn concentrations higher than 1 x 10.sup.18 cm.sup.-3, resulting in electron concentrations from 5 x 10.sup.17 to 2 x 10.sup.18 cm.sup.-3 at room temperature. For increasing free carrier concentrations, the electron mobility showed the tendency to increase from 10 to 30 cm.sup.2/Vs. The maximum mobility of 41 cm.sup.2/Vs, measured in a sample with free carrier concentration of 1 x 10.sup.18 cm.sup.-3, represents the highest value reported for β-Ga.sub.2O.sub.3 layers grown by MOVPE so far.

This PrimeView highlights how remote epitaxy may be used in the future to make flexible devices

Selective metal-AlGaN photodetectors based on the Schottky barrier and operating in UV spectral range have been developed. The selective photodiodes based on Ag-AlGaN Schottky barriers of different composition have been manufactured, which has made it possible to improve the photosensitivity in the UV spectral range and eliminate spurious signals in the long-wavelength part of the UV spectral range. This has made it possible to develop visible-blind photodetectors with the long-wavelength edge of photosensitivity lying at the wavelengths less than 350 nm. The width of the photosensitivity spectrum is within 15-40 nm, depending on the thickness of the Ag layer, which varies from 15 to 150 nm. The proper choice of the composition of the [Al.sub.x][Ga.sub.1 - x]N solid solution ensures increase in the photoresponse and reduction of the FWHM spectrum width up to 11 nm by matching peaks of the Ag transmission spectrum and the absorption spectrum of the epitaxial layer. The sensitivity is 0.071 A/W. The combination of effects of wideband window and over-the-barrier transfer has made it possible to create the ultraselective UV photodetectors based on Au-AlGaN structures with a half-width of the photosensitivity spectrum of 5-6 nm for the wave range 350-375 nm and a sensitivity of up to 140 mA/W. Based on a structure with the upper [Al.sub.x][Ga.sub.1 - x]N epitaxial layer (with the AlN content x = 0.1 or x = 0.06), selective photodetectors with the maximum photosensitivity at wavelengths of 355 nm and 362 nm have been developed. Application of an additional less wideband GaN layer has made it possible to independently control the short-wavelength and long-wavelength boundaries of the sensitivity range.

In recent times, due to their highly stable and radiation tolerant nature, interest toward feasibility of developing MAX phase-based applications has suddenly surged. In this context, we for the first time report a comprehensive spin-dependent transport study of Cr.sub.2AlC@p-Si-based thin film interfacial structure. Phase purity of the fabricated epitaxial Cr.sub.2AlC thin film grown by electron-beam deposition was confirmed from structural, vibrational and elemental analysis. Transport studies showed n-type metallic nature of the deposited Cr.sub.2AlC films. Low-temperature transport/magnetic measurements across the interface have shown spin-dependent Schottky behavior. Our results demonstrate the potential of Cr.sub.2AlC@p-Si as a novel Schottky interfacial structure for the development of more complex device applications.