Towards practical applications of quantum emitters in boron nitride

We demonstrate quantum emission capabilities from boron nitride structures which are relevant for practical applications and can be seamlessly integrated into a variety of heterostructures and devices. First, the optical properties of polycrystalline BN films grown by metalorganic vapour-phase epitaxy are inspected. We observe that these specimens display an antibunching in the second-order correlation functions, if the broadband background luminescence is properly controlled. Furthermore, the feasibility to use flexible and transparent substrates to support hBN crystals that host quantum emitters is explored. We characterise hBN powders deposited onto polydimethylsiloxane films, which display quantum emission characteristics in ambient environmental conditions.

Dependence of the V/III Ratio on Indium Incorporation in InGaN Films Grown by Metalorganic Vapour Phase Epitaxy

InGaN epitaxial layers were grown on c-plane sapphire substrates using the metalorganic vapour phase epitaxy (MOVPE) system at 760 °C. By varying the total flow rate of group-III sources (TMI+TEG) with a fixed molar ratio of group-III sources [TMI/(TMI+TEG)], the influence of V/III ratio were investigated from 4500 to 20000. The grown N-polar InGaN layers were investigated by atomic force microscopy and it is found that the surface roughness decreases with increasing the V/III ratios. High resolution X-ray diffraction analyses show that the phase separation decreases with increasing the V/III ratios. Photoluminescence measurements reveal that the peak position of the band-edge emission shifted toward the shorter wavelength with increasing the V/III ratios. Reciprocal space mapping (RSM) analyses were carried out on InGaN films. At low V/III ratio, the phase separation can be detected in InGaN films.

Advanced AlGaAs/GaAs Heterostructures Grown by MOVPE

AlGaAs/GaAs heterostructures are the base of many semiconductor devices. The fabrication of new types of devices demands heterostructures with special features, such as large total thickness (~20 μm), ultrathin layers (~1 nm), high repeatability (up to 1000 periods) and uniformity, for which a conventional approach of growing such heterostructures is insufficient and the development of new growth procedures is needed. This article summarizes our work on the metalorganic vapour-phase epitaxy (MOVPE) growth of AlGaAs/GaAs heterostructures for modern infrared devices. The growth approaches presented allow for the improved output characteristics of different emitting devices such as multi active region lasers, epitaxially integrated via highly doped tunnel junctions (emission wavelength λ ~ 1 μm), quantum cascade lasers (λ ~10 μm) and THz laser (λ ~100 μm), based on short-period superlattice with 500–2000 layers.

Tuning the Size, Shape and Density of γ′-GayFe4−yN Nanocrystals Embedded in GaN

Phase-separated semiconductor systems hosting magnetic nanocrystal (NCs) are attracting increasing attention, due to their potential as spintronic elements for the next generation of devices. Owing to their morphology- and stoichiometry-dependent magnetic response, self-assembled γ ’-Ga y Fe 4 − y N NCs embedded in a Fe δ -doped GaN matrix, are particularly versatile. It is studied and reported here, how the tuning of relevant growth parameters during the metalorganic vapour phase epitaxy process affects the crystalline arrangement, size, and shape of these self-assembled nanostructures. In particular, it is found that the Ga-flow provided during the δ -doping, determines the amount of Fe incorporated into the layers and the spatial density of the NCs. Moreover, the in-plane dimensions of the NCs can also be controlled via the Ga-flow, conditioning the aspect-ratio of the embedded nanostructures. These findings are pivotal for the design of nanocrystal arrays with on-demand size and shape, essential requirements for the implementation into functional devices.

Электролюминесценция одиночных InGaN/GaN микропирамид

The results of the fabrication of technological regimes of formation and the study of the optical properties of light emitting diodes (LED) micropyramids based on InGaN/GaN are presented. The structures were formed by the method of Metalorganic vapour-phase epitaxy. LED hetero structures based on single micropyramids demonstrate electroluminescence at a wavelength of 520–590 nm, which is shifted to the shortwave length region with increasing current pumping. These light-emission sources are of interest for the fabrication of high-intensity point light sources for biosensor applications.