Abstrakt
We used the transient-current technique to delineate the effects of different contact metals on the formation of space charge and on the profiles of the electric field in CdZnTe radiation detectors. In contrast to existing results on the polarization of semiconductor radiation detectors, we find that detectors with ohmic (Au/Au) contacts may experience a larger distortion of the internal electric field than those having Schottky (Au/In) contacts.
We explain this difference by postulating the presence of a deep hole trap (E_T) below the Fermi energy (E_F), which captures holes generated by the weakly injecting Au anode. The observed behaviour was described successfully by a numerical model relating the energy difference between E_T and E_F and the band bending at the contacts.
We also present results on aging effects that limit the detector's performance and stability over long times.