Electrical compensation in CdTe and CdZnTe by intrinsic defects

The effects of two intrinsic deep levels on electrical compensation and effects of dislocations on carrier mobility in semi-insulating CdTe and CdZnTe radiation detector crystals are reported here. These levels were found in samples grown by conventional Bridgman and high-pressure Bridgman techniques. The levels were observed with thermoelectric effect spectroscopy at distinct temperatures corresponding to thermal ionization energies of E-s1=0.27+/-0.07eV, E-d1=E-v+0.735+/-0.005eV and E-d2=E-v+0.743+/-0.005eV. The shallow level (E-s1) is associated with dislocations. The first deep level (Edl) is associated with the doubly ionized Cd vacancy acceptor and the second deep level (E-d2) is associated with the Te-antisite (Te-Cd). The second deep level (Te-Cd) was found to electrically compensate the material to produce high resistivity CdTe and CdZnTe, provided that the Cd vacancy concentration is sufficiently reduced during crystal growth or by post-growth thermal processing. The dislocations were found to affect the mobility of the carriers in the CdTe and CdZnTe crystals.