Charge-defect thermodynamic equilibrium and ‘‘metastable’’ defects in amorphous silicon

Abstract

A thermodynamic equilibrium description of the high-temperature (150–250 °C) steady-state behavior of light-induced defects in amorphous silicon is presented. The entropy and enthalpy of dangling-bond formation are quantified. In contrast to the behavior of vacancies in single-crystalline silicon the creation of the dangling-bond defect in amorphous silicon produces negative entropy and enthalpy changes indicating that lattice relaxations contribute to the free-energy changes. Over the temperature range examined, the creation of dangling bonds lowers the free energy due to the relatively large negative enthalpy change. Practical issues such as the estimation of the saturated dangling-bond density resulting from given illumination level at temperatures too low to experimentally observe true saturation are also considered.