The electrical activity of Ge dangling bonds is investigated at the interface between GeO2-passivated Ge( 1 1 1) substrate and Al2O3 grown by atomic layer deposition, by means of electrically detected magnetic resonance spectroscopy (EDMR). The Al2O3/GeO2/Ge stacked structure is promising as a mobility booster for the post-Si future electronic devices. EDMR proved to be useful in characterizing interface defects, even at the very low concentrations of state-of-the-art devices (< 10(10)cm(-2)). In particular, it is shown that capping the GeO2-passivated Ge( 1 1 1) with Al2O3 has no impact on the microstructure of the Ge dangling bond. (C) 2013 Elsevier B. V. All rights reserved.