Characterization of a strain-inducing defect in CdTe by magnetoluminescence spectroscopy.

Abstract

On the basis of the magnetoluminescence spectroscopy of a new isoelectronic defect complex in indium-doped CdTe the local structure and the associated strain direction are identified. This strain-inducing complex has a tetrahedral structure consisting of two substitutional indium atoms, one cadmium vacancy, and another cadmium atom. The Zeeman-effect experiments on the low-temperature photoluminescence are discussed in terms of a modified effective Hamiltonian. It is shown that the symmetry of the exciton binding trap is lower than trigonal. The bound exciton line at 1.584 19 eV (C line) is found to be associated with this complex and dominates the photoluminescence (PL) spectra in indium-doped CdTe. As many as 28 magnetic subcomponents in the PL spectra of the C line are resolved when the anisotropy of the Zeeman splitting is investigated. A modified perturbation Hamiltonian has led to an excellent agreement with the observed data. The C line is interpreted as a superposition of bound exciton recombinations from several inequivalent sets of tensionally strained defects with an angle of inclination \ensuremath{\tau}=2\ifmmode^\circ\else\textdegree\fi{} with respect to the trigonal [1,1,1] axis. The conduction-band g factor ${\mathit{g}}_{\mathit{e}}$=-1.73 and the valence-band parameters K=0.75, L=0.0 and the additional strain constant ratio W/D=-1.1 are to our knowledge the first values of this kind published for an isoelectronic trap with low symmetry. In zero magnetic field, the bound exciton recombinations from the inequivalent defects coincide, resulting in a luminescence line with only 0.12 meV half-width. We interpret the temperature quenching of the total emission intensity as a consequence of strain, induced by the defect complexes.