Improvement of the spectral response in large CdTe detectors operating at low bias voltage

This paper reports a method to improve the energy resolution for γ rays of a CdTe semiconductor detector 15 × 15 × 15 mm³ in size and with low applied voltage and an adequate electronic circuit constant. The principle of improvement is to make use of carrier trapping and ballistic defects. We investigated the improvement of the energy resolution by calculating the output waveforms using a Monte Carlo simulation. As a result, we could obtain an approximately 8% energy resolution of 662 keV equivalent to that of an NaI(Tl) scintillator. Further, the intrinsic efficiency of a full energy peak equivalent to that of a 1-in-thick cylindrical NaI(Tl) scintillator could be achieved. This method has the advantages that the energy spectra can be improved by simple systems and the noise is reduced because of the low leakage current due to the low applied voltage.