Lift-off of mesoporous layers by electrochemical etching on Si (100) substrates with miscut of 6° off towards (111)

• Published in: Thin solid films 2011-10, Vol.520 (1), p.606-609
• Main Authors: Garralaga Rojas, E., Terheiden, B., Plagwitz, H., Hensen, J., Wiedemeier, V., Berth, G., Zrenner, A., Brendel, R.
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Energy; Exact sciences and technology; Layer transfer; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Natural energy; Other semiconductors; Photovoltaic conversion; Photovoltaics; Physics; Porous Si; Solar cells. Photoelectrochemical cells; Solar energy; Specific materials; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Theory and models of film growth; Thin film structure and morphology; Thin-film
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2011.07.063

Uniform mesoporous Si double layers are formed on 4 inch p-type < 100> wafers with an off orientation of 6º towards < 111> by means of electrochemical etching in ethanoic-based HF electrolytes. These substrates are of interest for the epitaxial growth of III–V compound semiconductor stacks on their top for the production of multi-junction solar cells and very thin electronic devices. We demonstrate transfer of porous layers after an annealing process in hydrogen atmosphere. Electron Back-Scatter Diffraction analysis confirms that the substrate orientation is conserved during the etching and annealing steps. Confocal μ-Raman spectroscopy analysis shows a decrease in the Raman signal intensity after etching and a subsequent increase after annealing while no shift is observed. By means of Atomic Force Microscopy, analysis the surface appearance after the etching and annealing steps can be visualized. The mean surface roughness varies during the process from 0.55 nm for the unprocessed wafers to 0.27 nm after etching and 0.78 nm after annealing. The decrease of average roughness after etching is caused by an electropolishing step prior to porous formation. Despite of slight increase of mean surface roughness after annealing the samples are still appropriate for high quality epitaxial growth and subsequent lift-off.