Defects in Amorphous Semiconductors: Amorphous Silicon

Defects in disordered (amorphous) semiconductors are discussed, with an emphasis on hydrogenated amorphous silicon. The general differences between defect phenomena in crystalline and amorphous hosts are described, and the special importance of the electron–phonon coupling is stressed. Detailed calculations for amorphous Si are presented using accurate first principles (density-functional) techniques. The various approximations of ab-initio simulation affect aspects of the network structure and dynamics, and suitably accurate approximations are suggested. Defect dynamics and the motion of hydrogen in the network are reported.