Formation and electronic properties of the CdS/CuInSe2 (011) heterointerface studied by synchrotron-induced photoemission

Abstract

The heterointerface p-CuInSe2/CdS was investigated by soft x-ray photoelectron spectroscopy. CdS was deposited sequentially in steps onto CuInSe2 (011) cleavage planes at room temperature (RT) and at elevated temperatures (≳120 °C). At RT a nonreactive interface to cubic CdS is formed. The valence band and conduction-band discontinuities are determined to be 0.8 and 0.7 eV, respectively. A band bending of 0.9 eV is deduced for the p-type substrate. Annealing to temperatures above 120 °C leads to the formation of a CuxS reactive layer at the interface. As a consequence the valence-band offset and band bending is found to be considerably reduced. The experimentally determined band energy diagram is in agreement with heterojunctions of zincblende-type semiconductors, and its consequences for solar cells are discussed.