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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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AlGaAs surface reconstructions measured with RHEED along [110] and [ −110] azimuths at T=600 °C after minimization of the As flux at t=0 s. a (2 ×4) reconstruction at t=0 s, PAs=1×10−5 Torr. b (3 ×1) reconstruction at 0 s <t<tc, PAs≃2×10−8 Torr. c (4 ×2) reconstruction at t>tc, PAs≃1×10−8 Torr
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Fig2: AlGaAs surface reconstructions measured with RHEED along [110] and [ −110] azimuths at T=600 °C after minimization of the As flux at t=0 s. a (2 ×4) reconstruction at t=0 s, PAs=1×10−5 Torr. b (3 ×1) reconstruction at 0 s <t<tc, PAs≃2×10−8 Torr. c (4 ×2) reconstruction at t>tc, PAs≃1×10−8 Torr

Mentions: In the following, the evaporation of the topmost As reservoir on a (001) AlGaAs surface is studied with reflection high-energy electron diffraction during annealing at varied temperature T and low As pressure. The initial surfaces for the annealing experiments are stabilized by an As flux PAs=1.4×10−5 Torr and, thus, As-terminated. In the studied temperature range of T=590−650 °C in situ RHEED indicates a (2 ×4) reconstruction of the initial surface (Fig. 2a) which is expected for such conditions [21]. Assuming a γ(2 ×4) reconstruction [22], the initial As coverage of the topmost layer is about 1 ML.Fig. 2


Role of Arsenic During Aluminum Droplet Etching of Nanoholes in AlGaAs
AlGaAs surface reconstructions measured with RHEED along [110] and [ −110] azimuths at T=600 °C after minimization of the As flux at t=0 s. a (2 ×4) reconstruction at t=0 s, PAs=1×10−5 Torr. b (3 ×1) reconstruction at 0 s <t<tc, PAs≃2×10−8 Torr. c (4 ×2) reconstruction at t>tc, PAs≃1×10−8 Torr
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5037105&req=5

Fig2: AlGaAs surface reconstructions measured with RHEED along [110] and [ −110] azimuths at T=600 °C after minimization of the As flux at t=0 s. a (2 ×4) reconstruction at t=0 s, PAs=1×10−5 Torr. b (3 ×1) reconstruction at 0 s <t<tc, PAs≃2×10−8 Torr. c (4 ×2) reconstruction at t>tc, PAs≃1×10−8 Torr
Mentions: In the following, the evaporation of the topmost As reservoir on a (001) AlGaAs surface is studied with reflection high-energy electron diffraction during annealing at varied temperature T and low As pressure. The initial surfaces for the annealing experiments are stabilized by an As flux PAs=1.4×10−5 Torr and, thus, As-terminated. In the studied temperature range of T=590−650 °C in situ RHEED indicates a (2 ×4) reconstruction of the initial surface (Fig. 2a) which is expected for such conditions [21]. Assuming a γ(2 ×4) reconstruction [22], the initial As coverage of the topmost layer is about 1 ML.Fig. 2

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.