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.

GaNAs layers with a low As concentration (As ≤ 0.6%) have been grown by molecular beam epitaxy and studied by structural and optical methods. It has been observed that the incorporation of a small amount of As atoms into the GaN host leads to a significant reduction of the bandgap due to the formation of an As-related band above the valence band of the GaN host. The position of this band does not change with temperature, and therefore, a reduced temperature dependence of the bandgap is observed for As-diluted GaN compared to the pure GaN host, which is ∼40 meV vs ∼70 meV in the 10–295 K temperature range. The observed effect is explained within the band anticrossing model. It is expected that the reduced temperature dependence of the bandgap in As-diluted GaN can be utilized in lasers with improved thermal stability.