Evolution with time of the surface properties of high-purity germanium

The surface recombination velocity and the oxide film thickness on high-purity germanium have been investigated by photo-conductivity decay measurements and by ellipsometry after different chemical preparations. Depending on the etching, not only the surface recombination velocity was significantly changed but also its stability on exposure to air. In contrast, no direct correlation could be established between the surface recombination velocity and the surface oxide film thickness.