Compensation in semi-intrinsic CdTe based materials

In this report a brief review of the semi-intrinsic conductivity phenomenon in doped CdTe:Cl, CdTe:Ga and Cd 1 - x Zn x Te materials used for room temperature X and Υ- ray detectors is discussed. The upper limit of the resistivity is analysed in a framework of a general three-levels Fermi-statistic model. The role of the residual impurities and impurity-defect interaction as well as segregation of impurity in Te inclusions are discussed. Dependence of the elementary native defects energy formation on the Fermi-level position in CdTe is shown and some reactions between them are taken into consideration for the Fermi-level stabilisation near the middle of the band-gap. On the bases of the Fermi-level stabilisation phenomenon it is shown that a self-compensation and a maximum doping level in CdTe:Cl, CdTe:Ga and Cd 1 - x Zn x Te depend on the absolute energy of the C (V) -band position. Experimental results of EDAX compositional measurements, photoluminescence are used for illustration of these problems.