We identify a different type of deep donor DX center with orthorhombic ${\mathit{C}}_{2\mathit{v}}$ symmetry in III-V semiconductors. The center is predicted to occur only for anion site dopants, especially S. Its atomic structure, obtained from ab initio calculations, is characterized by cation-cation dimer-bond formation. Experimental data on S-doped GaAs and GaSb are shown to provide support for this type of DX structure. Theoretical results for DX centers with orthorhombic and trigonal symmetries in S-, Se-, and Te-doped GaSb, GaAs, and ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As alloys are examined. © 1996 The American Physical Society.

• Received 19 July 1996

DOI:https://doi.org/10.1103/PhysRevB.54.R14246