Formation of mesoporous germanium double layers by electrochemical etching for layer transfer processes

• Published in: Electrochemistry communications Vol. 12; no. 2; pp. 231 - 233
• Main Authors: Garralaga Rojas, E., Terheiden, B., Plagwitz, H., Hensen, J., Baur, C., Strobl, G.F.X., Brendel, R.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01-02-2010; Amsterdam Elsevier; New York, NY
• Subjects: Applied sciences; Electrochemistry; Energy; Exact sciences and technology; Natural energy; Photovoltaic conversion; Photovoltaics; Porous Ge; Solar cells. Photoelectrochemical cells; Solar energy; Electrochemistry; Porous Ge; Photovoltaics; Potential distribution; Electrochemical double layer; Photovoltaic system; Electrode electrolyte interface; Porous material; Mesoporosity; p type semiconductor; Hydrofluoric acid; Germanium; Electrochemical etching; Physicochemical properties
• ISSN: 1388-2481; 1873-1902
• DOI: 10.1016/j.elecom.2009.11.033

We produce uniform mesoporous single- and multilayers on 4
in.
p-type Ge wafers by means of electrochemical etching in highly concentrated HF-based electrolytes. Pore formation by anodic etching in germanium leads to a constant dissolution of the already formed porous layer plus substrate. Alternating the etching bias from anodic to cathodic bias enhances the passivation of the pore walls and substrate. The formation of porous multilayers is possible, since the starting layer is not dissolved during the formation of the separation layer. We report on the production of mesoporous double layers in Ge with different porosities. The change in the porosity of the porous layers is achieved by varying the anodic etching current and the HF concentration of the electrolyte. Porosities in the range of 25–65% are obtained for etching current densities of 1–15
mA
cm
−2 with the specific resistivity of the Ge substrates lying in the (0.020–0.032)
Ω
cm range and electrolyte HF concentrations in the range of 35–50
wt.%.