Deep levels in n-type high-purity (HP) detector grade germanium are studied using optical deep level transient spectroscopy (ODLTS). In this technique, optical injection (using light of above band gap energy) from the back ohmic contact together with a suitable sample configuration results in the detection of centers in the minority half of the band gap. Six deep minority carrier traps are detected in typical n-type HP germanium which turn out to be the same defects as found earlier in typical p-type HP germanium as majority carrier traps. These deep defects are mainly copper related. A formula is deduced to calculate concentrations from the ODLTS spectra. It is shown that in n- and p-type HP germanium not only the same defects are present but that their concentrations are also comparable.

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Optimization of the optical quality of optical-grade germanium components requires an in-depth investigation of the different contributions to the optical loss in germanium. In this paper we therefore focus on this optical characterization. We give an overview of possible characterization techniques to determine surface roughness, surface/bulk absorption and refractive index inhomogeneities and we highlight the obtained optical characteristics. To conclude we select the most appropriate non-destructive characterization tool for each optical parameter.

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