The effect of arsenic in improving lifetime in silicon-on-sapphire films

Abstract

Earlier workers reported a considerable increase in the lifetime of phosphorus-doped n -on-n+ silicon-on-sapphire (SOS) films. We report in this paper that a similar improvement in lifetime is obtained on arsenic-doped SOS film comprised of a higher-resistivity layer on top of a nondegenerate lower-resistivity layer. The significance of this work lies in that (a) from the device fabrication point of view arsenic is preferable because of its lower diffusion constant, and therefore will not out-diffuse during subsequent processing steps; and (b) a nondegenerate lower layer is sufficient to produce an improvement in lifetime. It is also shown that the generation lifetime τg increases exponentially with distance from the Al2O3–Si interface.