Semiconductors' efficiency: lithium dead layer detection of high-purity Germanium detectors

This study presents a mathematical model for the peak efficiency of a coaxial high-purity germanium detector using the Monte Carlo code (MCNP), based on data provided by the manufacturer. Consequently, the detector's model is optimized using a trial-and-error methodology, either by increasing/decreasing the dead layer thickness, aligning the peak efficiency results with experimental measurements. Results indicate that, over 15 years of continuous operation, the dead layer is approximately twice as thick as initially quoted by the manufacturer. Therefore, the dead layer results would confirm that it is crucial to regularly optimize the dead layer over time, as the operator needs to address potential occasional changes. The results indicate that the optimized MC model is suitable for calculating the activity of point/volumetric radioactive sources, with relative errors of 4.40 and 3.23%, respectively. Moreover, this work discusses the different factors that affect the accuracy of the absolute efficiency calibration of gamma spectrometers.