THE ZEEMAN-EFFECT ON BOUND-EXCITON STATES OF INDIUM-RELATED COMPLEX CENTERS IN CDTE

The PL spectrum of In-doped CdTe is known to exhibit, in many cases, a characteristic feature (the 'W line') at about 12780 cm-1 (almost-equal-to 1.584 eV), for which there are contradictory assignments in the literature. Using bulk CdTe:In crystals we have found that this feature appears after heat treatment in a Te atmosphere, accompanied by a decrease in the D0X emission. We have measured the Zeeman effect on the W line, including its dependence on the directions of magnetic field and polarization. These data show that this line originates from the annihilation of a two-particle bound exciton localized at trigonal complexes with symmetry axes parallel to the [111] directions. By analysing level splittings and relative transition probabilities on the basis of a standard spin Hamiltonian it is found that the trigonal impurity potential is due to a 'tensional' lattice deformation and the Zeeman spectra can be described quantitatively by the parameters g(e) = -1.7, K = 1.08, L = -0.1 and a = 0. Together with the magnitude of the diamagnetic shift, these values show that in the bound excitons the electron orbitals are rather extended and the hole orbitals are rather localized. In(i)-V(Cd), In(i)-A(Cd), or In(i)-3A(Cd) complexes (A being small-size acceptor impurities such as Li or Na) are considered to be the most probable candidates for the centres giving rise to the W line.