We present experimental data for the thermally activated capture of electrons on Si-induced impurity states in ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As in the strong-lattice-relaxation regime (DX centers). Experiments have been performed after photoionization in the region of transition from the normal to the metastable state of the defect, using hydrostatic pressure up to 8 kbars. An analysis of the isothermal as well as the thermostimulated capture kinetics strongly supports the hypothesis of the negative charge state of the DX Center.

• Received 28 February 1990

DOI:https://doi.org/10.1103/PhysRevLett.66.1737