Hydrogen Energetics and Transport Kinetics in Amorphous Silicon Hydride

Abstract

AbstractTo understand the electrical properties and behavior of amorphous silicon, it is imperative to understand the behavior of hydrogen in the amorphous silicon lattice. Although considerable effort has been extended to study hydrogen trapping in a-Si:H, the energetics and populations of the traps remain unresolved. We have developed a reaction diffusion model which includes multiple bulk trapping mechanisms, bulk transport, and realistic surface processes. The model results are compared with existing hydrogen temperature programmed evolution data, isothermal hydrogen evolution experiments, and thermal quenching experiments. We find consistently good fits for all three types of experiments with a shallow trap depth of 1.5 eV and deep trap depth of 1.8–1.9 eV below the mobility level, with 20–30% of hydrogen present in the deep trap. The difference of 0.3–0.4 eV between the two trap depths is similar to the defect formation activation energy and suggests a defect formation mechanism which involves movement of hydrogen from a deep to a shallow trap.