Photovoltaic effects in photoemission studies of Schottky barrier formation

Abstract

It is shown here that much of the recent photoelectron spectroscopy literature describing the onset of pinning in adsorbate–semiconductor systems at low temperature must be reinterpreted in light of surface photovoltaic effects. Two sources of surface charging are discussed, both of which are strongly enhanced at low temperature. The surface photovoltage resulting from separation of electron–hole pairs by the electric field in the depletion region is usually the dominant source of surface potential shifts, and causes flattening of the semiconductor bands. In addition, surface charging due to photoemission into the vacuum may reverse bias a p-type diode at low temperatures, causing increased band bending.