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

The size and distribution of built-in electric fields in $a-\mathrm{Si}:\mathrm{H}/a-\mathrm{Si}{\mathrm{N}}_x:\mathrm{H}$ 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 × ${10}^5$ V/cm in material with thin (12 Å) 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.