STATE OF DOPANT NICKEL IN CADMIUM TELLURIDE

A study has been made of the spectra of the impurity absorption and the photovoltaic current of CdTe crystals doped with nickel in the concentration range 10(18)-5 X 10(19) cm-3. It is found that the nickel is in two charge states: Ni2+ (3d8) and Ni+ (3d9). The energies found for the donor and acceptor states from the spectra of the photovoltaic current and the Hall effect are in reasonable agreement. However, the deep levels found cannot be assigned to pure impurity states. Since the susceptibility of CdTe:Ni crystals does not have a paramagnetic component, and since the compensation of free carriers is pronounced (n congruent-to p almost-equal-to 10(7)-10(8) cm-3 at T = 300 K), it is concluded that neutral complexes form. The depth of these complexes has been determined.