Local-vibrational-mode spectroscopy ofDXcenters in Si-doped GaAs under hydrostatic pressure

We report the observation of a local vibrational mode (LVM) in hydrostatically stressed, Si-doped GaAs. The corresponding infrared absorption peak is distinct from the ${\mathrm{Si}}_{\mathrm{Ga}}$ shallow-donor LVM peak and is assigned to the Si DX center. The relative intensities of the Si DX LVM and the Si shallow-donor LVM peaks and photoquenching behavior of the sample are consistent with the appearance of a defect which binds two electrons as it undergoes a large lattice relaxation at approximately 23 kbar.