Al2O3, ZrO2, and Al2O3/ZrO2/Al2O3 high-k dielectric stacks are grown on germanium substrates by atomic layer deposition at temperatures of 150 and 300 degrees C. The electrical properties of the films are compared in terms of substrate preparation and deposition temperature. We demonstrate that a deposition on germanium-oxide-free substrates by using HBr-etching pretreatment yields a much higher breakdown voltage of the high-k oxide compared to HF- or HCl-type pretreatments. Further, we show that the deposition of dielectrics at lower temperatures (150 degrees C) leads to decreased leakage currents in the range of about I order of magnitude and to lower inversion capacitances at high measurement frequencies. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3205455] All rights reserved.