DEFECT EQUILIBRIUM IN SEMIINSULATING CDTE(CL)

The Hall coefficient R(H) and conductivity sigma were measured in the temperature range 250-450 K in semi-insulating Cl-doped CdTe crystals. Due to the high electron mobility, a reversal of sign of R(H) appears at 370 K. A simultaneous analysis of R(H)(T) and sigma(T) was performed with the help of theoretically determined mobilities and Hall factors of both electrons and heavy holes. It yields a position of the deep level connected with the second charge state of a divalent cadmium vacancy E(a2) = 0.69 eV above the valence band and the position of Fermi level E(F) = - E(g) + E(a2) + 0.72 k0T pinned to E(a2). Using these values total concentrations of defects and the energy necessary for the creation of the neutral complex (VCdClTE)x almost-equal-to 1.06 eV were determined on the basis of a detailed point defect model, which describes the association of cadmium vacancies and chlorine atoms. The energy liberated by the compensation of chlorine donors by these complexes (almost-equal-to 1.20 eV) is sufficient for the generation of these complexes so that a strong compensation occurs at a growth temperature of 450-degrees-C for Te-rich conditions.