High Purity Germanium Based Radiation Detectors with Segmented Amorphous Semiconductor Electrical Contacts: Fabrication Procedures

Abstract: Radiation detectors constructed from large volume high purity Ge (HPGe) single crystals are widely used for gamma-ray spectroscopy. The detectors for this application can be simple in that they need only have two electrical contacts for voltage application and signal readout. Such HPGe based detectors have been commercially produced for many decades using standard semiconductor fabrication processes. For the applications of gamma-ray imaging and particle tracking, however, interaction position measurement within the detector as well as the measurement of the deposited energy is required. This necessitates a more complex detector often with the electrical contacts divided into a large number of segments that can be individually instrumented for signal readout. The reliable and cost-effective implementation of contact segmentation with the standard commercial processes is a challenge. An alternative fabrication technology based on thin film amorphous semiconductor layers was developed at Lawrence Berkeley National Laboratory (LBNL) and can be used to produce finely segmented, fully passivated HPGe detectors. Over the last almost two decades, a large number of segmented contact HPGe detectors have been produced at LBNL using this technology. This paper provides a set of procedures that has been used at LBNL for the manufacture of the segmented amorphous semiconductor contact HPGe detectors.