X-ray and ultraviolet photoelectron spectroscopy measurements of Cu-doped CdTe(111)-B:: Observation of temperature-reversible CuxTe precipitation and effect on ionization potential

Temperature-programmed x-ray photoelectron spectroscopy (TP-XPS) and ultraviolet photoelectron spectroscopy (UPS) measurements of CdTe(111)-B are used to probe changes to the surface electronic structure that accompany heavy Cu dopant levels and CuxTe precipitation. UPS measurements reveal that the ionization potential of the heavily Cu-doped substrate is only slightly smaller than that of the undoped material. Also, temperature-reversible CuxTe precipitation is observed, which lowers the ionization potential of the surface from 5.7 eV to 4.8 eV. These results suggest that interfacial CuxTe precipitation might play a key role in ohmic-contact formation in CdTe-based photovoltaic devices. (c) 2007 American Institute of Physics.