HYDROGENATED AMORPHOUS-SILICON THIN-FILMS DEPOSITED BY TRIODE ASSISTED REACTIVE SPUTTERING

Thin films of hydrogenated amorphous silicon have been deposited for solar cell and other device applications. If device quality thin films can be deposited by triode assisted sputtering, more control over film properties can be achieved than with the more thoroughly studied glow discharge and magnetron sputtering techniques. The results reported here are on films with many properties which are equivalent to those of device quality materials. These hydrogenated amorphous silicon films were all intrinsic and were deposited under a variety of H-2:Ar ratios and substrate temperatures. The best results were on films deposited at 240-degrees-C and hydrogen contents in the range of 11%-20%. The films were characterized by means of thermal evolution studies to determine hydrogen content, Fourier transform infrared transmission spectroscopy to determine the H-2 bonding modes, van der Pauw dark conductivity and photoconductivity measurements, ultraviolet/visible light absorption to determine the band gap, scanning electron microscopy studies to determine film surface quality, and Auger and secondary ion mass spectroscopy in order to determine the surface and bulk impurity levels. Films grown to a thickness of about 1-mu-m had light to dark conductivity ratios greater than 5 X 10(4), band gaps of 1.78 eV and they exhibited the monohydride bonding configuration, all of which are results characteristic of device quality films.