ZnO:Sb MBE layers with different Sb content-optical, electronic and structural analysis

Abstract

Understanding how Sb atoms are located in the ZnO crystal lattice and how they affect the layer parameters is essential to obtain p-type conductivity in ZnO:Sb. In this paper, the results of our extensive research (XPS, Raman, X-Ray, SIMS) of Sb doped ZnO films grown by Molecular Beam Epitaxy are presented. It is shown with use of high resolution X-ray Photoemission Spectroscopy (XPS) that three charge states of the Sb impurity: Sb3+, Sb5+, and Sb3− can exist in ZnO:Sb layers. The dominant charge state of Sb ions is 3 + while the contribution of 5 + is very low. The relative fraction of Sb atoms located at the Zn sites is about ∼90%, while ∼10% are incorporated in oxygen sites. It was found that increasing the Sb content in the layers increases the intensity of Raman modes at 511 cm−1, 533 cm−1, and 575 cm−1, which confirms their correlation with Sb doping. Additionally, a blue shift of the E2High Raman mode of ZnO was observed, related to the increase of strain in the oxygen sublattice. The relation between strain and stress for different Sb chemical states (Sb3+, Sb5+, Sb3−) in ZnO is calculated and compared with experimental results.