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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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Calculated time-dependent a Al adatom density nAl, b As adatom density nAs, and c droplet volume VD. The process parameters are T=605 °C, ND=4.8×108, and varied FAs and nAs(0) as indicated. FAl=0.4 ML/s for t<tG=2.5 s (growth) and FAl=0 for t>tG (annealing). The As flux FAs in ML/s and the initial As adatom density nAs(0) in ML are varied as indicated
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Fig6: Calculated time-dependent a Al adatom density nAl, b As adatom density nAs, and c droplet volume VD. The process parameters are T=605 °C, ND=4.8×108, and varied FAs and nAs(0) as indicated. FAl=0.4 ML/s for t<tG=2.5 s (growth) and FAl=0 for t>tG (annealing). The As flux FAs in ML/s and the initial As adatom density nAs(0) in ML are varied as indicated

Mentions: Model calculations for droplet growth and post-growth annealing are performed by numerically solving Eqs. 1–3 with the initial conditions VD(0)=0,nAl(0)=0, and nAs(0)= 0 or 1 ML. As an example, Fig. 6 shows calculation results for T=605 °C, FAl= 0.4 ML/s during growth and zero during annealing, tG=2.5 s, and ND=3×107 cm −2. FAs and nAs(0) are varied as indicated. The chosen model parameters are EAl,S=1.0 eV, EAl,E= 1.5 eV, and EAlAs=2.1 eV.Fig. 6


Role of Arsenic During Aluminum Droplet Etching of Nanoholes in AlGaAs
Calculated time-dependent a Al adatom density nAl, b As adatom density nAs, and c droplet volume VD. The process parameters are T=605 °C, ND=4.8×108, and varied FAs and nAs(0) as indicated. FAl=0.4 ML/s for t<tG=2.5 s (growth) and FAl=0 for t>tG (annealing). The As flux FAs in ML/s and the initial As adatom density nAs(0) in ML are varied as indicated
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Fig6: Calculated time-dependent a Al adatom density nAl, b As adatom density nAs, and c droplet volume VD. The process parameters are T=605 °C, ND=4.8×108, and varied FAs and nAs(0) as indicated. FAl=0.4 ML/s for t<tG=2.5 s (growth) and FAl=0 for t>tG (annealing). The As flux FAs in ML/s and the initial As adatom density nAs(0) in ML are varied as indicated
Mentions: Model calculations for droplet growth and post-growth annealing are performed by numerically solving Eqs. 1–3 with the initial conditions VD(0)=0,nAl(0)=0, and nAs(0)= 0 or 1 ML. As an example, Fig. 6 shows calculation results for T=605 °C, FAl= 0.4 ML/s during growth and zero during annealing, tG=2.5 s, and ND=3×107 cm −2. FAs and nAs(0) are varied as indicated. The chosen model parameters are EAl,S=1.0 eV, EAl,E= 1.5 eV, and EAlAs=2.1 eV.Fig. 6

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.