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Reliable p-doped hexagonal boron nitride (h-BN) could enable wide bandgap optoelectronic devices such as deep ultra-violet light emitting diodes (UV LEDs), solar blind photodiodes and neutron detectors. We report the study of Mg in h-BN layers as well as Mg h-BN/AlGaN heterostructures. Mg incorporation in h-BN was studied under different biscyclopentadienyl-magnesium (Cp2Mg) molar flow rates. 2θ-ω x-ray diffraction scans clearly evidence a single peak, corresponding to the (002) reflection plane of h-BN with a full-width half maximum increasing with Mg incorporation in h-BN. For a large range of Cp2Mg molar flow rates, the surface of Mg doped h-BN layers exhibited characteristic pleats, confirming that Mg doped h-BN remains layered. Secondary ion mass spectrometry analysis showed Mg incorporation, up to 4 × 1018 /cm3 in h-BN. Electrical conductivity of Mg h-BN increased with increased Mg-doping. Heterostructures of Mg h-BN grown on n-type Al rich AlGaN (58% Al content) were made with the intent of forming a p-n heterojunction. The I-V characteristics revealed rectifying behavior for temperatures from 123 to 423 K. Under ultraviolet illumination, photocurrent was generated, as is typical for p-n diodes. C-V measurements evidence a built-in potential of 3.89 V. These encouraging results can indicate p-type behavior, opening a pathway for a new class of wide bandgap p-type layers. [ABSTRACT FROM AUTHOR]

Highlights from the article: Keywords: 2D boron nitride; core/shell nanostructures; flexible electronics; nanorods; semiconductors; van der Waals epitaxy In article number 1900207, Suresh Sundaram, Abdallah Ougazzaden, and co-workers demonstrate self-organized GaN nanorods formation on layered h-BN templates by van der Waals epitaxial growth. Nanorods, semiconductors, flexible electronics, core/shell nanostructures, van der Waals epitaxy, 2D boron nitride.

Hexagonal boron nitride (h‐BN) is a promising 2D template that decouples substrate effects from the layer above it by van der Waals epitaxy, because there are only weak forces out of the h‐BN. It also permits convenient mechanical transfer of devices grown on their surface to an appropriate substrate. Here, van der Waals epitaxial growth resulting in the formation of self‐organized GaN nanorods on h‐BN templates is demonstrated. This approach to the growth of III‐N nanostructures avoids transfer processes and scaling issues seen with other 2D materials, since both the 1D (GaN nanorods) and 2D (h‐BN) are grown at the wafer‐scale and in one growth run. Further, this process is used to grow vertical core–shell p‐GaN/InGaN/n‐GaN nano‐PIN device structures on wafer‐scale 2D h‐BN on sapphire and silicon substrates. The high quality of the core–shell nanostructures is confirmed by detailed electron microscopy study, which gives more insight into the nanorod formation mechanism on 2D material. Mechanical transfer of nanostructures on sapphire substrates to copper tape is then demonstrated, with no resulting damage of nanorods. Use of MOVPE grown large‐area h‐BN to realize nanostructures is a significant advancement and can lead to new nanodevice architectures needed for next‐generation optoelectronic devices. [ABSTRACT FROM AUTHOR]

Highlights • h-BN were grown on sub-micron size dome patterned sapphire substrates. • Wrinkled morphology of layered h-BN was obtained on c -plane sapphire. • On the domes, h-BN were different demonstrating anisotropy. • TEM confirmed h-BN is layered and continuous with turbostratic islands on domes. • 320 nm peak intensity increase confirms the TEM observations. Abstract Layered h-BN were grown on sub-micron size dome patterned sapphire substrates (PSS) by metal organic vapor phase epitaxy (MOVPE) to study the effects of substrate orientations, strain and subsequent thermal stress evolution. Electron micrograph images on the surface of the c -plane sapphire in-between the dome structures show typical wrinkled morphology of layered h-BN, similar to the reference sample surface confirming the high quality h-BN growth. However, the h-BN morphology on the domes exhibited pattern like folding which were drastically different from the h-BN on the c -plane sapphire. Detailed TEM studies show that the h -BN is layered and covers the dome patterns of the sapphire substrates like a "blanket of snow" continuously with localized strain variations induced turbostratic phase insertions. In addition, the local variation in optical emission properties of layered materials, which are dramatically affected by the rippled morphology were also investigated using depth resolved cathodoluminescence. The intensity variation of the 320 nm peak confirms that the BN on dome structures have more strain related defects than the c -plane h-BN. Thus, these results give better insight on the origin of turbostratic BN grains and local control over the structural and optical emission characteristics. [ABSTRACT FROM AUTHOR]

Highlights • Demonstrated growth and mechanical exfoliation of MQWs on h-BN templates. • Obtained satellite peaks on the MQWs structure on h-BN indicating good periodicity. • Good heterointerface quality was confirmed with TEM analysis. • Depth resolved CL shows double MQW emission peaks. • After lift-off CL analysis confirmed good preservation of optical functionalities. Abstract We report wafer-scale growth and mechanical exfoliation of 20 periodAl 0.58 Ga 0.42 N/Al 0.37 Ga 0.63 N multiple quantum wells (MQWs) on h-BN buffered templates and compare them to control samples of the same structure on AlN templates. X-ray diffraction measurements of the MQW structure on h-BN clearly featured satellite peaks up to third order in the 2θ−ω scans indicating good MQW periodicity. Detailed transmission electron microscope (TEM) analysis show good heterointerface quality in the structure and large V-pits on the surface. Depth resolved cathodoluminescence of the MQWs on h-BN revealed a UV emission peak at 299 nm and a sharp shoulder at 292 nm. We also report lift-off and transfer of the MQW on the h-BN structure and have investigated post-transfer optical emission, which demonstrates good preservation of optical emission characteristics. Together these results show the suitability of h-BN buffers for the realization of free-standing or flexible optical devices emitting in the deep UV region. [ABSTRACT FROM AUTHOR]