Chapter 3 Hydrogenation of Defects in Crystalline Silicon

Abstract

This chapter discusses the hydrogenation of defects in crystalline silicon. It describes the structural defects in crystalline silicon, the most obvious being the discontinuity of the crystal at the surface. Such a surface is covered with dangling bonds that can be terminated by monatomic hydrogen, with the dramatic consequence of a greatly reduced surface recombination. Internal surfaces that contain dangling bonds, such as grain boundaries, microvoids, and dislocations, are also affected by hydrogenation. Because dangling bonds are sites for generation–recombination processes, their removal by hydrogenation is very beneficial to silicon devices, in particular to polycrystalline Si solar cells. The chapter describes the passivation of surface states and of bulk dangling bonds, including grain boundaries, dislocations, and point defects. A grain boundary, the interface between two adjacent crystallites, is the site of many dangling bonds. These dangling bonds pin the Fermi level near midgap at the interface.