Photoluminescence of CuGaTeAs and CuGaSnGa complexes in n-GaAs under resonance polarized excitation

Photoluminescence (PL) of n-type GaAs:Te:Cu and GaAs:Sn:Cu with an electron density of about 1018 cm−3 was studied at 77 K. A broad band with a peak at the photon energy near 1.30 eV (GaAs:Te:Cu) or 1.27 eV (GaAs:Sn:Cu) was dominant in the PL spectrum under interband excitation. This band arose from the recombination of electrons with holes trapped by CuGaTeAs or CuGaSnGa complexes. It has been found that the low-energy edge of the excitation spectrum of this PL band at photon energies below ∼1.4 eV is controlled by the optical ejection of electrons from a complex into the conduction band or to a shallow excited state. The PL polarization factors upon excitation by polarized light from this spectral range suggest that the complexes have no additional distortions caused by an interaction of a hole bound at the center in the light-emitting state with local phonons of low symmetry. This feature makes CuGaTeAs and CuGaSnGa complexes different from those with the Ga vacancy (VGa) instead of CuGa. The dissimilarity arises from the difference in the intensity of interaction of a hole localized at the orbital of an isolated deep-level acceptor in the state corresponding to its preemission state in the complex (CuGa− and VGa2−) with low-symmetry vibrations of atoms. The perturbation of the hole orbital induced by the donor in the complex practically does not affect this interaction.