Superior resolution:

Superior resolution of these detectors can resolve much more complex gamma ray spectra than those obtained by Nal (TI) detectors as shown in Figure where much sharper lines are observed. Usually resolution of the order of ~1.5 keV at 1332 keV of ⁶⁰Co peak is observed though recently still better resolution detectors have become available. However, these detectors have lower efficiency compared to NaI (Tl) detectors. It is a common practice to refer efficiency of a semiconductor detector as relative to a standard 3"× 3" NaI (Tl) detector with a point source of

Figure: Comparison of gamma ray spectra of ¹³⁷Cs and ⁶⁰Co sources recorded with scintillation gamma ray spectrometer and high resolution gamma ray spectrometer

activity at a distance of 25 cm from the detector. All the semiconductor detectors have low dead times and are relatively insensitive to magnetic fields. Their disadvantages include the necessity for liquid nitrogen cooling, small size of the output signal and their higher cost compared to scintillation gamma ray spectrometers. Ge (Li) or HPGe detector is always used in conjunction with an MCA and thus spectrum cannot be recorded manually.