Abstract

Hydrogenated, amorphous silicon (a-Si:H) is of great interest for thin film devices used, for example, for the transformation of photon energy and as semiconductor material. Important applications are thin film solar cells, thin film transistors for liquid crystal displays, photoreceptors for electrophotography and laser printing and image sensors. To improve and optimize the properties of the material for specific applications it is necessary to control the formation of the three dimensional network during the solidification process ("bandgap engineering"). Incorporation of hydrogen into the network reduces the density of defects near the middle of the bandgap ("gap states"). For optimal performance a specific binding configuration should be realized. Distortions in the metastable silicon network, especially in the bond angle, are believed to be responsible for the tail states at the bandgap edges. Since these defect states constitute traps for charge carriers and thus lower their mobilities it is necessary to reduce the density of these states. To achieve an efficient control of the deposition process in this direction, detailed molecular information on the dynamic processes leading to solidification and on the structure-performance relationship is needed.

© 1991 Optical Society of America