1. Alloying during local droplet etching of AlGaAs surfaces with aluminium
- Author
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Wiebke Hansen, Ch. Heyn, and M. Zocher
- Subjects
010302 applied physics ,Fabrication ,Materials science ,Analytical chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,Substrate (electronics) ,021001 nanoscience & nanotechnology ,01 natural sciences ,chemistry ,Etching (microfabrication) ,Quantum dot ,Aluminium ,0103 physical sciences ,Melting point ,Molecule ,0210 nano-technology ,Phase diagram - Abstract
Local droplet etching (LDE) drills self-assembled nanoholes into AlGaAs surfaces and represents a powerful technique for the fabrication of versatile quantum structures like quantum dots, rings, and molecules. Usually, LDE is performed at temperatures T = 600 − 680 ° C if Al is used as the etching material. Now, atomic force microscopy establishes that Al-LDE drills nanoholes also at very low temperatures down to T = 360 ° C which is 300 ° C below the melting point of bulk Al. Several possible etching mechanisms like a melting-point depression, solid-state etching, and alloying are discussed. Selective wet-chemical etching experiments using HF indicate significant alloying with Ga from the substrate, and thus the formation of Al-Ga droplets for etching. The upper limit of x ≤ 50 % for the Al content inside the Al-Ga droplets is indicated by the selectivity of the HF acid. This value is in agreement with an estimation of x = 0.42, which is based on the measured droplet and hole volumes. A comparison with the Al-Ga phase diagram indicates that a completely liquid phase of the droplets is essential for etching.
- Published
- 2019