Molecular beam epitaxial growth of ZnCdTeO epilayers for intermediate band solar cells

We report the growth and characterization of the lattice-matched Zn1-xCdxTe1-yOy (ZnCdTeO) layers on ZnTe substrates by radio frequency plasma-assisted molecular beam epitaxy technique. The Cd composition increases linearly with increasing Cd/(Zn+Cd) flux ratio, indicating a controllability of Cd composition by Cd flux. Introduction of O radical during the growth of ZnCdTe resulted in the formation of ZnCdTeO layer. At particular O and Cd compositions lattice-matched ZnCdTeO epilayers on ZnTe substrate were obtained. Photoreflectance (PR) spectroscopy on the lattice-matched ZnCdTeO layer revealed two distinct PR features in the energy regions at 2.2–2.5eV and 1.5–1.8eV, which can be attributed to transitions from the valence band to the two conduction subbands, E+ and E−, respectively. ► Highly-mismatched ZnCdTeO layers were epitaxially grown on ZnTe substrates. ► Lattice-matched ZnCdTeO layer was obtained at particular O and Cd compositions. ► Transition energies related to intermediate band were determined.