Linear x-ray detector array made on bulk CdZnTe for 30∼100 keV energy

A CdZnTe detector grown by the high pressure Bridgman (HPB) growth technique was tested using high energy x-rays (30∼100 keV), and the performance was compared with a commercially available Nal scintillating detector of 5 cm thickness. The charge collection efficiency of a CdZnTe detector is as high as 90% at relatively low electric field, 600 V/cm. At high x-ray photon energies, the detection efficiency is reduced due to the thickness of the CdZnTe. A 32 channel linear array was fabricated on 1.2∼1.7 mm thick CdZnTe, of which the detector area was 175 × 800 μm² and the pitch size 250 μm. The measured dark current for the 16 element detector was as low as 0.1 pA at 800 V/cm with an excellent uniformity. Energy spectra were measured using a Co⁵⁷ radiation source. A small pixel effect and charge sharing were observed. The energy resolution was improved and compared with the large area detector. The array detector gave an average 5.8% full-width-half-maximum (FWHM) at 122 keV photopeak. The large area detector of the same material before fabrication exhibited a low energy tail at the photopeak, which limits the photopeak FWHM to 8%.