The locally restricted motion of hydrogen and deuterium which are trapped at Cd acceptors in silicon has been studied by perturbed-angular-correlation spectroscopy. Close Cd-H and Cd-D pairs were identified by their characteristic electric-field gradients. The kinetics of these complexes was extracted directly from the time spectra. In the temperature region between 270 and 430 K clear evidence has been found for thermally activated motion of hydrogen or deuterium about the Cd with an activation energy of 0.21 eV for both hydrogen as well as deuterium. The isotropic-mass-dependent attempt frequencies are in the order of ${10}^9$ ${\mathrm{s}}^{\mathrm{-}1}$. The ratio of the frequency for hydrogen relative to that for deuterium is ${\nu }_{\mathrm{H}}$/${\nu }_{\mathrm{D}}$=3.3(1.3).

• Received 28 February 1991

DOI:https://doi.org/10.1103/PhysRevLett.67.847