Microinhomogeneities in Semi-Insulating Cd(Zn)Te

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We investigated the temperature dependences (TDs) in the range of 290-423 K for the Hall constant RHand the Hall carrier mobility μn(σ RH) in semi-insulating Cd0.9Zn0.1Te:In (CZT) crystals. As-grown, CZT material has nonequilibrium distributions of native and impurity-related defects. Thus, before taking any measurements, the samples were kept inside the test chamber in the dark at 423 K to reach an equilibrium state at THTD could be described by two activation energies. At the transitional point, the TD of the carrier mobility also changes from “normal” at high temperatures to “exponential” at low temperatures. The latter is a result of the collective effect of drift barriers due to microinhomogeneity. Therefore, only the high-temperature activation energies can be assigned to the ionization energies of the compensated deep donors (εD). For different samples, the values for εD0(at absolute zero) were found to be in the range of 0.50-0.78 eV, and the degree of donor compensation [D+]/[D] is between 0.3 and 0.98. The low-temperature region, where there are strong effects of crystal microinhomogeneities, cannot be used to characterize the ionization energy of donors. Therefore, we describe the activation energy as ε1= εD- αεb, where εbis the drift barrier height found from the TD of the carrier mobility and α takes a value close to unity. Values of εbfor our studied samples lie within (0.05-0.35) eV.