Suppressing the polarization effect in high temperature conditions for an In/CdTe/Pt detector

CdTe diode detectors have an instability called "polarization effect". The polarization makes difficult maintaining the performances of CdTe detectors without some depolarization methods in high temperature conditions. The technique of periodical turning off the bias voltage has been developed to depolarize the detector (called "refreshing"). The refreshing periods and the pulsed off times were investigated to maintain the spectral performance in the temperature range of 50°C to 70 °c. The energy resolutions for a 662 keY photo peak were evaluated. The bias voltage of -600 V was applied to the 9.7 × 5 × 2.2 mm, In/CdTe/Pt planar detector. The higher temperature required the shorter refreshing period to obtain good energy resolutions. When the turning off time was fixed to be 30 ms, the following refreshing periods were required to obtain the energy resolution within 2.5%; below 10 s at 50°C, below 2 s at 60°C and 0.5 s at 70°C. However, a frequent refreshing caused the increase of the dead time. Then both the refreshing period and the pulsed off time were shortened. As a result, even at 70 °C, both the energy resolution within 2.5% and the dead time of 1% were found to be compatible. This implies the detectors can be used in the wide temperature range.