ANOMALOUS RELAXATION OF LIGHT-INDUCED STATES OF A-SI-H

For a large variety of B, P doped and undoped a-Si:H films, we observe d the non-monotonic kinetics of structural changes at elevated tempera tures (above 100 degrees C), indicating the coexistence of two process es described by stretched exponentials. While the faster process has c haracteristics corresponding to the conventional metastable dangling b ond creation, the characteristics of the slow process are shown to be anomalous (the activation energy for defect creation larger than that for the normal process and the parameter, beta, decreasing with temper ature). To describe the anomalous process, we propose a phenomenologic al model based on a three-level configuration-coordinate diagram with correlated activation energies for the light-induced metastable state creation and annealing. The model accounts for the observed features o f the anomalous process. A possible underlying microscopic mechanism o f structural changes is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.