Characterization of chemically modified CdTe surfaces

Abstract

Chemical modification of CdTe by ruthenium ions has been shown to reduce the surface recombination velocity and thus increase the effective diffusion length of minority carriers. X-ray photoelectron spectroscopy, secondary ion mass spectrometry and Raman scattering measurements have been used to examine the physical nature of the surface layers, showing the presence of a thin layer of tellurium on unmodified surfaces, which is replaced by a thicker layer of TeO₂ on modification. Electrochemical photocapacitance spectroscopy demonstrates directly the removal of mid-gap states and the creation of band-edge states on matte etching and Ru modification.