TETRAHEDRALLY SYMMETRICAL DX-LIKE STATES OF SUBSTITUTIONAL DONORS IN GAAS AND ALXGA1-XAS ALLOYS

The structural and electronic properties of Si, Ge, Sn, S, Se, and Te substitutional donors in GaAs are examined via self-consistent pseudopotential calculations. Two distinct negatively charged DX-like deep donor states are found. The first has a broken-bond atomic configuration while the second arises from a symmetric "breathing-mode" relaxation around the impurity. The energies of the two configurations are especially close for Sn, Se, and Te donors. Experimental data on DX centers in A1xGa1-xAs alloys are analyzed within this model.