Hydrogen on semiconductor surfaces

The state of understanding concerning hydrogen at semiconductor surfaces (external and internal) will be reviewed, the emphasis being on silicon and germanium. Topics will include hydrogen at crystalline-vacuum interfaces in ultra-high-vacuum systems, at grain boundaries in polycrystalline material, and at internal defect surfaces as arise in irradiated or ion-implanted material. The atomic configurations of hydrogen in semiconductors will be surveyed, including both monoatomic hydrogen (H) and molecular hydrogen (H2). The diffusion coefficients and profiles associated with free (H) diffusion, trapping of (H) at defects, and formation of (H2) will be covered. The role of hydrogen in passivating defects will be discussed, as will the passivation mechanisms (bonding and non-bonding), and defect/surface reconstruction and chemically driven reconstruction