Aluminum in complex luminescence defects in irradiated silicon

Two aluminum-related defect spectra in irradiated silicon, Al1 with a no-phonon transition at 0.836 eV and Al2 at 0.886 eV, are studied by photoluminescence measurements employing temperature control and perturbation spectroscopy with uniaxial stress and magnetic fields. Al1 is a defect of rhombic I (C_2v) site symmetry, probably incorporating carbon in addition to aluminum. Its optical properties are very similar to those of the Ga1 and T defects (related to Ga and C or B and C, respectively), suggesting equivalent microscopic structure of the Al1, Ga1, and T defects. For Al2, monoclinic I (C_1h) or trigonal (C_3v) symmetry is found in stress or Zeeman measurements, respectively, with annealing behavior and local modes similar to Al1.