Defect-state engineering in a-Si:H: An effective tool for studying processes during light-induced degradation

Charge deep-level transient spectroscopy (Q-DLTS) has proved to be a powerful tool for investigating the defect-state distribution in hydrogenated amorphous silicon (a-Si:H) in both annealed and light-soaked states. In this article, we report on Q-DLTS experiments that were designed to further investigate our recently published model for the Staebler-Wronki effect (SWE). By subjecting an a-Si:H based metal/oxide/semiconductor structure to negative (positive) bias voltage during the annealing above the equilibration temperature a programmed p-type (n-type) defect-state distribution can be established in the undoped a-Si:H layer. In this way defect-state engineering in a-Si:H is achieved that enables us to study the role of different components of the defect-state distribution in the light-induced degradation process. Additional possibility to control the role of a particular defect-state component in the degradation process is to apply a bias voltage also during light soaking. The observed changes in the programmed defect-state distributions due to light soaking under various conditions give additional information on the SWE and can be interpreted with our model for the SWE.