Defect equilibrium in semi-insulating CdTe(Cl)

Abstract

Abstract The Hall coefficient R H and conductivity σ 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 gs ( 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 k 0 T pinned to E a2 . Using these values total concentrations of defects and the energy necessary for the creation of the neutral complex (V Cd Cl TE ) x ≈ 1.06 eV were determined on the basis of 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 (≈ 1.20 eV) is sufficient for the generation of these complexes so that a strong compensation occurs at a growth temperature of 450°C for Te-rich conditions.