Hydrogen Diffusion in Silicon - An ab initio Study of Hydrogen Kinetic Properties in Silicon

TL;DR

This study uses ab initio DFT calculations to determine hydrogen defect migration and decomposition barriers in silicon, revealing that hydrogen molecules do not significantly contribute to hydrogen diffusion.

Contribution

It provides detailed kinetic properties of hydrogen defects in silicon, clarifying the role of hydrogen molecules and ions in diffusion processes, which was previously misunderstood.

Findings

Hydrogen ions are the dominant migrating species with a barrier of 0.46 eV.

Hydrogen molecules decompose at higher temperatures with barriers of 1.2 and 1.5 eV.

Hydrogen molecules do not participate in hydrogen transport in silicon.

Abstract

In this paper we present kinetic properties such as migration and decomposition barriers of hydrogen defects in silicon calculated by Density Functional Theory (DFT) based methods. We study the following defects: H atoms (H) and ions (H+, H-), hydrogen molecules (H2) and hydrogen complexes (H2*). Our results show that the dominating migration species are H ions, their charge-independent migration barrier being 0.46 eV in excellent agreement with experimental value [1]. At higher temperatures H2 and H2* decompose with barriers of 1.2 and 1.5 eV respectively, while the migration barrier of H2 is 2.2 eV. Hence, we show that, contrary to what has been experimentally implied [2, 3] previously, in silicon, hydrogen molecules do not participate to the hydrogen transport through diffusion. 1. A. Van Wieringen and N. Warmoltz, Physica 22, 849 (1956). 2. S. Rao, S. K. Dixit, G. Lupke, N. H. Tolk, and L. C. Feldman, Physical Review B 75, 6 (2007). 3. N. Fukata, A. Kasuya, and M. Suezawa, Physica B 308, 1125 (2001).