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Role of Arsenic During Aluminum Droplet Etching of Nanoholes in AlGaAs

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ABSTRACT

Self-assembled nanoholes are drilled into (001) AlGaAs surfaces during molecular beam epitaxy (MBE) using local droplet etching (LDE) with Al droplets. It is known that this process requires a small amount of background arsenic for droplet material removal. The present work demonstrates that the As background can be supplied by both a small As flux to the surface as well as by the topmost As layer in an As-terminated surface reconstruction acting as a reservoir. We study the temperature-dependent evaporation of the As topmost layer with in situ electron diffraction and determine an activation energy of 2.49 eV. After thermal removal of the As topmost layer droplet etching is studied under well-defined As supply. We observe with decreasing As flux four regimes: planar growth, uniform nanoholes, non-uniform holes, and droplet conservation. The influence of the As supply is discussed quantitatively on the basis of a kinetic rate model.

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Schematic cross-section of a (001) AlGaAs surface with Ga/Al (red) and As (blue) atoms. Dashed spheres mark lattice atoms. As atom (1) illustrates desorption from the As surface reservoir. The deposited As atom (2) can re-evaporate or react with an Al adatom. The mobile Al atom (3) is generated by deposition or detachment from a droplet and can attach to a droplet or react with an As atom. The corresponding rates are discussed in the text
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Fig4: Schematic cross-section of a (001) AlGaAs surface with Ga/Al (red) and As (blue) atoms. Dashed spheres mark lattice atoms. As atom (1) illustrates desorption from the As surface reservoir. The deposited As atom (2) can re-evaporate or react with an Al adatom. The mobile Al atom (3) is generated by deposition or detachment from a droplet and can attach to a droplet or react with an As atom. The corresponding rates are discussed in the text

Mentions: Figure 3 shows measured values of tc as function of the substrate temperature T. The data establish a clear decrease of tc with increasing T. For a quantitative analysis, we assume a thermally activated arsenic desorption rate RAs,D=ν exp[−EAs,D/(kBT)] (Fig. 4), with a vibrational frequency ν, an activation energy EAs,D, and Boltzmanns constant kB. The experimental data are well reproduced by a thermally activated rate, where an arsenic desorption-related activation energy EAs,D=2.49 eV is determined by an Arrhenius fit.Fig. 3


Role of Arsenic During Aluminum Droplet Etching of Nanoholes in AlGaAs
Schematic cross-section of a (001) AlGaAs surface with Ga/Al (red) and As (blue) atoms. Dashed spheres mark lattice atoms. As atom (1) illustrates desorption from the As surface reservoir. The deposited As atom (2) can re-evaporate or react with an Al adatom. The mobile Al atom (3) is generated by deposition or detachment from a droplet and can attach to a droplet or react with an As atom. The corresponding rates are discussed in the text
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037105&req=5

Fig4: Schematic cross-section of a (001) AlGaAs surface with Ga/Al (red) and As (blue) atoms. Dashed spheres mark lattice atoms. As atom (1) illustrates desorption from the As surface reservoir. The deposited As atom (2) can re-evaporate or react with an Al adatom. The mobile Al atom (3) is generated by deposition or detachment from a droplet and can attach to a droplet or react with an As atom. The corresponding rates are discussed in the text
Mentions: Figure 3 shows measured values of tc as function of the substrate temperature T. The data establish a clear decrease of tc with increasing T. For a quantitative analysis, we assume a thermally activated arsenic desorption rate RAs,D=ν exp[−EAs,D/(kBT)] (Fig. 4), with a vibrational frequency ν, an activation energy EAs,D, and Boltzmanns constant kB. The experimental data are well reproduced by a thermally activated rate, where an arsenic desorption-related activation energy EAs,D=2.49 eV is determined by an Arrhenius fit.Fig. 3

View Article: PubMed Central - PubMed

ABSTRACT

Self-assembled nanoholes are drilled into (001) AlGaAs surfaces during molecular beam epitaxy (MBE) using local droplet etching (LDE) with Al droplets. It is known that this process requires a small amount of background arsenic for droplet material removal. The present work demonstrates that the As background can be supplied by both a small As flux to the surface as well as by the topmost As layer in an As-terminated surface reconstruction acting as a reservoir. We study the temperature-dependent evaporation of the As topmost layer with in situ electron diffraction and determine an activation energy of 2.49 eV. After thermal removal of the As topmost layer droplet etching is studied under well-defined As supply. We observe with decreasing As flux four regimes: planar growth, uniform nanoholes, non-uniform holes, and droplet conservation. The influence of the As supply is discussed quantitatively on the basis of a kinetic rate model.

No MeSH data available.


Related in: MedlinePlus