Measurement of the CdSe/ZnTe valence band offset by x-ray photoelectron spectroscopy

We have used x-ray photoelectron spectroscopy (XPS) to measure the valence band offset in situ for CdSe/ZnTe (100) heterojunctions grown by molecular-beam epitaxy. XPS measurements were performed for films of CdSe (100) and ZnTe (100), and for heterojunctions consisting of either ∼25 Å of CdSe grown on ZnTe or ∼25 Å of ZnTe grown on CdSe. Observations of reflection high energy electron diffraction patterns indicated that CdSe films deposited on ZnTe were grown in cubic zinc blende form, rather than the natural wurtzite structure of CdSe. Our measurements yielded a CdSe/ZnTe valence band offset ΔEv=0.64±0.07 eV. The corresponding conduction band offset for CdSe/ZnTe is ΔEc=1.22±0.07 eV for room temperature band gaps for ZnTe and for cubic CdSe of 2.25 and 1.67 eV, respectively.