A NOVEL PREPARATION TECHNIQUE FOR PREPARING HYDROGENATED AMORPHOUS-SILICON WITH A MORE RIGID AND STABLE SI NETWORK

A novel preparation technique, termed "chemical annealing," was developed with the aim of making a stable and rigid Si network structure. The hydrogen content (C(H)) in the films and the optical gap could be reduced gradually without any change in substrate temperature by alternating deposition of a hydrogenated amorphous silicon layer several tens of angstrom thick and treatment with atomic hydrogen. These films showed C(H) of 1.5-10 at. %, and exhibited high photoconductivities in the level of 10(-5)-10(-4) S/cm. In the films with C(H) of 3 at. % or less, in particular, improvement was observed in stability against illumination with light. Their photoconductivity remained at about 65% of the initial value even after illumination with white light (AM1, 100 mW) for 60 h. In addition, time-of-flight experiments revealed a significant enhancement in hole drift mobility to a value of 0.2 cm2/V s at 300 K.