Comparison of the x-ray spectroscopy response and charge transport properties of semi-insulating In/Al doped CdZnTe crystals

The x-ray spectroscopy performance of In/Al doped CdZnTe planar detectors based on as-grown crystals were investigated at room temperature, using a Tb x-ray source with a principle energy of 44.2 keV. The observed broadening in the photopeak resolution was attributed to incomplete charge carrier collection due to carrier trapping and scattering by the defects in the crystal. Alpha particle spectroscopy and pulse shape rise time analysis were used to measure the electron mobility lifetime product ͑͒, as well as the mobility ͑͒ of the CdZnTe material grown with different dopant concentrations. To further clarify the role of the dopant and associated trapping states, temperature dependent alpha particle spectroscopy and pulse shapes were investigated at various applied bias fields over a temperature range from 200 to 300 K. CdZnTe doped with 1.5 ppm In exhibits excellent x-ray spectral resolution and charge transport properties, which implies a lower density of trapping centers in the crystal. The deep levels associated with Cd i 2+ have been tentatively recognized as electron trapping centers and this is confirmed by the observed reduction in electron lifetime in CdZnTe crystal with 15 ppm In. Additionally, a shallower electron detrapping defect, with an activation energy of 0.14Ϯ 0.02 eV, was also discovered to be simultaneously present in the crystal. In 30 ppm Al doped CdZnTe, however, the carrier mobility was significantly degraded due to scattering of the ionized centers attributed to the aluminum interstitial Al i