The schematic shows a STM tip scanning over a c(6×12) reconstructed GaN(0001) surface at liquid helium temperature (-451 degrees F).
Dr. Arthur Smith’s article on “Native Gallium Adatoms Discovered on Atomically-Smooth Gallium Nitride Surfaces at Low Temperature” was named an ACS Editors’ Choice and provided as part of the open access initiative.
A limited number of peer-reviewed research articles from ACS journals are selected as Editors’ Choice. The selection of these articles is based on recommendations by the scientific editors of ACS journals from around the world. The selected articles remain open access.
Smith is Professor of Physics & Astronomy at Ohio University. The article was published in Nano Letters.
Abstract: In advanced compound semiconductor devices, such as in quantum dot and quantum well systems, detailed atomic configurations at the growth surfaces are vital in determining the structural and electronic properties. Therefore, it is important to investigate the surface reconstructions in order to make further technological advancements. Usually, conventional semiconductor surfaces (e.g., arsenides, phosphides, and antimonides) are highly reactive due to the existence of a high density of group V (anion) surface dangling bonds. However, in the case of nitrides, group III rich growth conditions in molecular beam epitaxy are usually preferred leading to group III (Ga)-rich surfaces. Here, we use low-temperature scanning tunneling microscopy to reveal a uniform distribution of native gallium adatoms with a density of 0.3%–0.5% of a monolayer on the clean, as-grown surface of nitrogen polar GaN(0001̅) having the centered 6 × 12 reconstruction. Unseen at room temperature, these Ga adatoms are strongly bound to the surface but move with an extremely low surface diffusion barrier and a high density saturation coverage in thermodynamic equilibrium with Ga droplets. Furthermore, the Ga adatoms reveal an intrinsic surface chirality and an asymmetric site occupation. These observations can have important impacts in the understanding of gallium nitride surfaces.
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