Evidence for Lattice-Mismatch—Induced Defects in Amorphous Semiconductor Heterojunctions

Abstract

The size and distribution of built-in electric fields in $a\ensuremath{-}\mathrm{Si}:\mathrm{H}/a\ensuremath{-}\mathrm{Si}{\mathrm{N}}_{x}:\mathrm{H}$ layered amorphous semiconductor materials have been determined by use of electroabsorption spectroscopy. Strong asymmetries are present between the interfaces, leading to internal fields as large as 4 \ifmmode\times\else\texttimes\fi{} ${10}^{5}$ V/cm in material with thin (12 \AA{}) layers. These fields are due to an interface charge present when amorphous silicon is deposited onto silicon nitride, which we attribute to strain-relieving defects caused by structural mismatch.