Microscopic theory of hydrogen in silicon devices

Incorporation of hydrogen has a strong effect on the characteristics of silicon devices. A fundamental understanding of the microscopic mechanisms is required in order to monitor and control the behavior of hydrogen. First-principles calculations hare been instrumental in providing such understanding. We first outline the basic principles that govern the interaction between 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 motion of hydrogen through the material, as relating to diffusion and defect formation. We also discuss the enhanced stability of Si-D compared to Si-H bonds, which mar provide a means of suppressing defect generation. We present a microscopic mechanism for hydrogen-hydrogen exchange, and examine the metastable =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 computational electronics will also be discussed.