We have examined the influence of bismuth (Bi) and nitrogen (N) fluxes on N and Bi incorporation during molecular-beam epitaxy of GaAs1-x-yNxBiy alloys. The incorporation of Bi is found to be independent of N flux, while the total N incorporation and the fraction of N atoms occupying non-substitutional lattice sites increase with increasing Bi flux. A comparison of channeling nuclear reaction analysis along the [100], [110], and [111] directions with Monte Carlo-Molecular Dynamics simulations indicates that the non-substitutional N primarily incorporate as (N-As)As interstitial complexes. We discuss the influence of Bi adatoms on the formation of arsenic-terminated [110]-oriented step-edges and the resulting enhancement in total N incorporation via the formation of additional (N-As)As.
We have examined the formation mechanisms of GaN quantum dots (QDs) via annealing of Ga droplets in a nitrogen flux. We consider the temperature and substrate dependence of the size distributions of droplets and QDs, as well as the relative roles of Ga/N diffusivity and GaN nucleation rates on QD formation. We report on two competing mechanisms mediated by Ga surface diffusion, namely QD formation at or away from pre-existing Ga droplets. We discuss the relative roles of nucleation and coarsening dominant growth, as well as the polytype selection, on various substrates. The new insights provide an opportunity for tailoring QD size and polytype distributions for a wide range of III-N semiconductor QDs.__________________________ 1) H. Lu and C. Reese contributed equally to this work. 2) Corresponding Author: rsgold@umich.eduIn recent years, quantum dots (QDs) based on gallium nitride (GaN) and its alloys have been demonstrated for a wide variety of device applications, such as solar cells, 1 ,2 lightemitting diodes, 3,4,5 lasers, 6,7 and single-photon emitters. 8,9 QDs are typically grown epitaxially via a strain-induced Stranski-Krastanov (S-K) growth mode transition, which leads to a misfitstrain induced polarization in the QDs. 10 On the other hand, the nucleation and conversion of QDs via nitridation of metallic droplets, known as droplet epitaxy (DE), has attracted much attention as misfit-strain-induced-polarization is expected to be minimized. To date, DE of GaN QDs has been demonstrated on a variety of substrates, including 6H-SiC(0001), 11Si (111), 12,13,14 AlGaN/6H-SiC(0001), 15 and c-Al2O3, 16 with single electron transistor achieved on AlN/3C-SiC(001). 17 Furthermore, understanding of DE is critical for elucidation of the mechanisms for GaN growth under Ga-rich conditions, which are often argued to be a version of liquid phase epitaxy. 18 Indeed, during Ga-rich GaN growth, the low solubility of carbon in Ga and the reactivity of oxygen in Ga, with subsequent desorption of GaO at growth temperatures, leads to low carbon 19 and oxygen 20 co-incorporation. Therefore, DE GaN QDs are expected to be superior to those grown by the SK method. 21 However, conflicting results have been reported regarding the formation mechanisms of DE GaN QDs. For example, Wang et al. 17 and Gherisimova et al. 22 reported on the formation of QDs via a liquid phase epitaxy (LPE)-like process, where GaN crystallizes along the substrate/droplet interface when N supersaturates the liquid Ga. On the other hand, Debnath et al. 15 proposed a surface diffusion-driven mechanism, where Ga diffuses away from the droplets and reacts with N on the surface to form small QDs. Finally, Kawamura et al. 23 and Otsubo et al. 24 propose a formation mechanism where N diffuses along the surface to the droplet edges, and small QDs nucleate at the periphery. Here, we investigate the formation mechanisms for DE GaN QDs using a combined computational-experimental approach. Our first-principles calculations of activation barriers suggest that N is immobi...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.