Hexagonal boron nitride (h-BN), together with other members of the van der Waals crystal family, has been studied for over a decade, both in terms of fundamental and applied research. Up to now, the spectrum of h-BN-based devices has broadened significantly, and systems containing the h-BN/III-V junctions have gained substantial interest as building blocks in, inter alia, light emitters, photodetectors, or transistor structures. Therefore, the understanding of electronic phenomena at the h-BN/III-V interfaces becomes a question of high importance regarding device engineering. In this study, we present the investigation of electronic phenomena at the h-BN/GaN interface by means of contactless electroreflectance (CER) spectroscopy. This nondestructive method enables precise determination of the Fermi level position at the h-BN/GaN interface and the investigation of carrier transport across the interface. CER results showed that h-BN induces an enlargement of the surface barrier height at the GaN surface. Such an effect translates to Fermi level pinning deeper inside the GaN band gap. As an explanation, we propose a mechanism based on electron transfer from GaN surface states to the native acceptor states in h-BN. We reinforced our findings by thorough structural characterization and demonstration of the h-BN/GaN Schottky diode. The surface barriers obtained from CER (0.60 ± 0.09 eV for GaN and 0.91 ± 0.12 eV for h-BN/GaN) and electrical measurements are consistent within the experimental accuracy, proving that CER is an excellent tool for interfacial studies of 2D/III–V hybrids.
Nano‐ and micro‐rods of GaN offer many functionalities that are not present in regular flat nanostructures. Therefore, development of new growth methods of such structures is a hot topic. In this work the arsenic‐induced growth of GaN microrods under Ga‐rich conditions in the molecular beam epitaxy is presented. It is a self‐catalyst vapor–liquid–solid process with native Ga droplets. The formation of Ga droplets is induced by antisurfactant properties of arsenic. The presence of As during the epitaxial process promotes the growth of dodecagonal microrods with 12 walls: six m‐planes and six a‐planes. It is possible since As changes the growth rates for the different GaN planes comparing to arsenic‐free conditions, where hexagonal microrods are usually formed. The growth parameters and their influence on the sample morphology are carefully studied in this work. Microrods with an average height and diameter of 3 and 0.7 µm, respectively, and the density of 2.3 × 107 cm−2, are obtained under optimal growth conditions. The observed mechanism of growth of microrods can also be present in other material systems by introducing atoms with antisurfactant properties under metal‐rich conditions, where the surface is covered by a metal monolayer.
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