PHOTOEMISSION-STUDY OF CDS HETEROJUNCTION FORMATION WITH BINARY SELENIDE SEMICONDUCTORS

Synchrotron radiation soft x-ray photoemission spectroscopy was used to investigate the development of the electronic structure at the CdS/Cu2-xSe and CdS/In6Se7 heterojunction interfaces. Cu2-xSe and In6Se7 layers were deposited on GaAs (100) by physical vapor deposition from Cu2Se and In2Se3 sources. CdS overlayers were then deposited in situ, at room temperature, in steps on these layers. Photoemission measurements were acquired after each growth to observe changes in the valence-band electronic structure and changes in the In4d and Cd4d core lines. The results were used to correlate the interfacial chemistry with the electronic structure and to directly determine the CdS/Cu2-xSe and CdS/In6Se7 heterojunction valence-band discontinuities and the consequent heterojunction band diagrams. These results are compared to the valence-band offset (Delta E(v)) for the CdS/CuInSe2 heterojunction interface.