The research focus of the group is the study of defects in semiconductor materials in order to explain their effects on electrical and optical properties of semiconductor devices. The semiconductors in research focus are Si, Ge, diamond, III-V, II-VI and Cu(In/Ga)Se2, with applications in microelectronics, optoelectronics and photovoltaics (solar cells). Defects are investigated trough their electronic and vibrational (local vibrational modes (LVM)) and electron magnetic resonance spectra. We aim at obtaining physical properties, structural identification and quantification of defects via various electrical characterization and (quasi) spectroscopic techniques. Special attention is given to defect determination at the edge of the detection limits. The characterization techniques that are used are electron paramagnetic resonance (EPR, in collaboration with the EMR group), Fourier-transform infrared spectroscopy (FTIR) and Deep-level transient spectroscopy (DLTS).