Arsenic‐Induced Growth of Dodecagonal GaN Microrods with Stable a‐Plane Walls

Abstract

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.

Role of Temperature in Arsenic-Induced Antisurfactant Growth of GaN Microrods

“…These observations are consistent with the result obtained from the microrod grown at 800 °C. 29 The longer, smooth edge corresponds to a -planes of the GaN structure and the shorter rough edges correspond to m -planes. Moreover, this result proves that arsenic is not built into the structure of the microrod, which confirms the hypothesis that the signal observed from XRD measurements assigned to the GaNAs layer originates from layers growing between rods and not rods itself.…”

“…In order to study the temperature influence on the growth process, all other growth parameters were kept constant between processes. Samples were grown under a beam equivalent pressure of Ga equal to 4.3 × 10 –7 mbar, a high arsenic overpressure above 1 × 10 –6 mbar, and a nitrogen flux of 5 sccm with a plasma power of 500 W. According to our previous research, these parameters are optimal for the formation of GaN microrods . The growth temperature was varied in steps of 40 °C from 720 °C up to 880 °C.…”

“…In our previous work, the growth parameters such as gallium and arsenic fluxes were determined to have a vital influence on the growth mode regime. 29 It was shown that obtaining columnar growth is possible only in Ga-rich conditions under high arsenic overpressure. These growths were performed at an arbitrary chosen temperature of 800 °C, which is close to the optimal growth temperature of high-quality GaN layers.…”

“…Recently, our studies showed that the growth of dodecagonal GaN microrods with dominating a -planes is possible by arsenic-induced vapor–liquid–solid (VLS)–MBE growth . It is well-known that critical parameters in all MBE growth processes are the III/V elements ratio and substrate temperature.…”

“…In our previous work, the growth parameters such as gallium and arsenic fluxes were determined to have a vital influence on the growth mode regime . It was shown that obtaining columnar growth is possible only in Ga-rich conditions under high arsenic overpressure.…”