Metals on cadmium telluride: Schottky barriers and interface reactions

Abstract

The Schottky barriers formed for a wide range of metals on (110) n-CdTe surfaces have been studied using current-voltage and capacitance-voltage techniques. The surfaces were prepared by cleaving in ultrahigh vacuum, cleaving in air, and chemical etching. The electrical barriers are drastically influenced by oxide layers on the surface. Most metals on the chemically etched surfaces yield barriers having values around 0.7 eV but Mn, Cr, and V are notable exceptions, yielding ohmic or low barrier contacts. Microscopic interactions of these interfaces have also been studied by soft x-ray photoemission using synchrotron radiation. Detailed comparisons of the microscopic interaction of Ag and Mn with the clean and oxidized surfaces, using photoemission, are presented. In contrast to the behavior of Ag, the Mn overlayer completely reduces the CdTe native oxide layer, resulting in lower barrier contacts.