Microscopic theory of hydrogen in silicon devices

Incorporation of hydrogen has a strong effect on the characteristics of sil icon devices. A fundamental understanding of the microscopic mechanisms is required in order to monitor and control the behavior of hydrogen. First-pr inciples calculations hare been instrumental in providing such understandin g. We first outline the basic principles that govern the interaction betwee n hydrogen and silicon, followed by an overview of recent first-principles results for hydrogen interactions with silicon. We show that H-2 molecules are far less inert than previously assumed. We then discuss results for mot ion of hydrogen through the material, as relating to diffusion and defect f ormation. We also discuss the enhanced stability of Si-D compared to Si-H b onds, which mar provide a means of suppressing defect generation. We presen t a microscopic mechanism for hydrogen-hydrogen exchange, and examine the m etastable =SiH2 complex formed during the exchange process. Throughout, we highlight issues relevant for hydrogen in amorphous silicon (used in solar cells, sensors and displays) and in Si-SiO2 structures (used in integrated circuits). The broader impact of first-principles calculations on computati onal electronics will also be discussed.