Preparation of Inclusion and Precipitate Free Semi-Insulating CdTe

Annealing conditions used for the preparation of semi-insulating CdTe after elimination of inclusions and precipitates are discussed. Second phase defects are eliminated by post-growth stoichiometric annealing and the semi-insulating CdTe is prepared by re-annealing under Te or Cd overpressure. In case of In-doped samples with high In concentration, semi-insulating CdTe with resistivity approximately 10⁹ Omegacm was prepared by annealing under Te overpressure. In-situ high temperature measurement of the electrical conductivity and Hall coefficient is used to find annealing conditions for undoped and slightly In-doped CdTe. The dominant extrinsic acceptor level with a concentration of N_A = 4 times 10¹⁵ cm^-3 was determined and Cd-rich annealing was used for the preparation of semi-insulating CdTe.