Abstract. Photoluminescence (PL) of stain-etched crystalline Ge and a-SiGe:H thin films is observed at room temperature. Scanning electron microscopy reveals that the etched materials have a rough surface morphology which depends on the chemical systems used. The position of the PL peaks depends both on the chemical systems used and the resistivity of the Ge crystalline wafers. Raman spectra suggest that trigonal GeO₂ (which contains hydrogen and OH groups) is present on the treated Ge surface. It is assumed that a chemical compound based on Ge is obtained as a result of the stain-etched Ge and it is responsible for the visible PL observed.

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