The unique physical, mechanical, chemical, optical, and electronic properties of hexagonal boron nitride (hBN) make it a promising two-dimensional material for electronic, optoelectronic, nanophotonic, and quantum devices.

Here we report on the changes in hBN's properties induced by isotopic purification in both boron and nitrogen. Previous studies on isotopically pure hBN have focused on purifying the boron isotope concentration in hBN from its natural concentration (approximately 20 at% 10 B, 80 at% 11 B) while using naturally abundant nitrogen (99.6 at% 14 N, 0.4 at% 15 N), i.e. almost pure 14 N. In this study, we extend the class of isotopically-purified hBN crystals to 15 N. Crystals in the four configurations, namely h 10 B 14 N, h 11 B 14 N, h 10 B 15 N, and h 11 B 15 N, were grown by the metal flux method using boron and nitrogen single isotope (>99%) enriched sources, with nickel plus chromium as the solvent.

In-depth Raman and photoluminescence spectroscopies demonstrate the high quality of the monoisotopic hBN crystals with vibrational and optical properties of the 15 N-purified crystals at the state of the art of currently available 14 N-purified hBN. The growth of high-quality h 10 B 14 N, h 11 B 14 N, h 10 B 15 N, and h 11 B 15 N opens exciting perspectives for thermal conductivity control in heat management, as well as for advanced functionalities in quantum technologies.

The luminescence efficiency of AlxGa1−xN quantum dots (QDs) and quantum wells (QWs), buried in AlN cladding layers and emitting in the ultraviolet range between 234 and 310 nm, has been investigated. The growth and optical properties have been done using similar aluminum composition (varying from 0.4 to 0.75) for both QDs and QWs. In order to compare as much as possible the optical properties, the QWs were fabricated with a growth time tuned such that the QW width is similar to the average height of the QDs. The photoluminescence (PL) showed emission ranging from 4 to 5.4 eV, putting into evidence differences in terms of full width at half maximum, PL intensity, and asymmetry of the line shape between QDs and QWs. The results show shorter wavelengths and a slightly narrower PL linewidth for QWs. To determine the light emission dependence with the electric field direction in the crystal, the evolutions of the emission diagrams for all samples were recorded along two orthogonal directions, namely, the “in-plane” (growth) and the “on-side” directions, from which the light emission was collected. For the whole QDs and QWs samples' series, the shapes of the emission diagram indicate emission in both in-plane and on-side directions, as evidenced by intra-valence band mixings caused by strain effects combined with the anisotropic Coulomb interactions that are particularly contributing to the polarization at wavelengths below 260 nm. Furthermore, the degree of polarization, determined for each sample, showed good agreement with results from the literature.

Controlling the electrical properties of SiC requires knowledge of the nature and properties of extended defects. We have employed orthodox defect-selective etching and photo-etching methods to reveal typical and new structural defects in commercial SiC wafers. For photo-etching, the etch rate increases as the free carrier concentration decreases. The etch rate can be used to estimate the free carrier concentration with higher precision, and over a larger lateral and depth range than that accessed by Raman scattering. The logarithmic dependence of the etch rate on the free carrier concentration has been characterized.