Localisation of the p-n junction in poly-silicon thin-film diodes on glass by high-resolution cross-sectional electron-beam induced current imaging

Abstract

High-resolution scanning electron microscope, focused ion beam (FIB) microscope, and electron-beam induced current (EBIC) images are taken on large-grained polycrystalline silicon thin-film diodes on glass. To aid understanding of the plan-view EBIC images obtained, trenches are cut into the diodes in the FIB microscope, and the p-n junction then located and examined in the diode's cross section using high-resolution EBIC. Diffusion of aluminium atoms from the heavily doped emitter region into the base region of the diode along grain boundaries during material fabrication is found to have locally altered the junction's location and therefore alters the EBIC signal in these regions. Using this method allows a fast and easy location of the p-n junction in these diodes, in addition to aiding in the identification of unusual junction deviations which complicate the interpretation of plan-view EBIC images.