Amorphous hydrogenated silicon-nitrogen (a-Si/sub 1-x/N/sub x/:H) films deposited by PECVD

Abstract

Hydrogenated amorphous silicon-nitrogen (a-Si/sub 1-x/N/sub x/:H) thin films are interesting for optoelectronic applications. The optical gap of this material varies in the range from 1.8 to 3 eV depending mainly on the nitrogen content. The electronic, optical and structural properties are influenced by the technological parameters. The authors deposited hydrogenated amorphous silicon-nitrogen thin films by the use of Plasma Enhanced Chemical Vapour Deposition (PECVD). The system consisted of an ultra high vacuum chamber equipped with 13.56 MHz RF generator, separate gas lines with gas flow meters, turbomolecular pumps with automatic pressure control and a precise temperature regulator. It was possible to obtain 10/spl times/10 cm/sup 2/ homogeneous films with reproducible properties in a silane-ammonia gas mixture, Optical, structural, chemical composition and electrical properties of a-Si/sub (1-x)/N/sub x/:H were examined by optical and infrared spectroscopy, conductivity and photoconductivity measurements. The films revealed the monotonic increase in optical gap value with nitrogen content increase. The nitrogen rich samples exhibit low photoconductivity and a wide bandgap. These materials could substitute for hydrogenated amorphous silicon for such applications as solar cells or photodetectors.