Symmetry of Donor-Related Centers Responsible for Persistent Photoconductivity inAlxGa1−xAs

Abstract

We report on the attenuation of ballistic phonons generated in bulk GaAs and propagating through epitaxial layers of ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ containing up to ${10}^{18}$ Sn or Te donors per cubic centimeter. The latter donors are known to form a complex with an unidentified defect (DX center) whose occupation is changed by photoexcitation. The symmetry of the ionized DX center is shown to be trigonal in the case of Sn and most likely orthorhombic in the case of Te donors.