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 (