Domain Matching Epitaxial Growth of High-Quality ZnO Film Using a Y₂O₃ Buffer Layer on Si (111)

High-quality ZnO epitaxial films have been grown by pulsed-laser deposition on Si (111) substrates using a nanothick high-k oxide Y2O3 buffer layer. Determined by X-ray diffraction and transmission electron microscopy, the epitaxial relationship between ZnO and Y2O3 follows (0001)⟨21̅1̅0⟩ZnO||(111)⟨101̅⟩Y2O3. ZnO lattice aligns with the hexagonal O sublattice in Y2O3 and the interfacial structure can be well described by domain matching epitaxy with 7 or 8 ZnO {112̅0} planes matching 6 or 7 {44̅0} planes of Y2O3 and lead to a significant reduction of residual strain. Superior optical properties were obtained even for ZnO films as thin as 0.21 μm from photoluminescence results

Exciton Localization of High-Quality ZnO/Mg_<i>x</i>Zn_1–<i>x</i>O Multiple Quantum Wells on Si (111) with a Y₂O₃ Buffer Layer

We report the structural and optical properties of ten-period ZnO/Mg_<i>x</i>Zn_1–<i>x</i>O multiple quantum wells (MQWs) prepared on the most widely used semiconductor material, Si. The introduction of a nanometer thick high-k Y₂O₃ transition layer between Si (111) substrate and a ZnO buffer layer significantly improves the structural perfection of the MQWs grown on top of it. The high structural quality of the ZnO/Mg_<i>x</i>Zn_1–<i>x</i>O MQWs is evidenced by the appearance of pronounced high order satellite peaks in X-ray crystal truncation rods; high resolution cross-sectional transmission electron microscopy images also confirmed the regularly arranged well and barrier layers. When the well width is less than ∼2.7 nm, the quantum-confined Stark effect in MQWs can be negligible. Not only the increasing exciton-binding energy but also reducing exciton–phonon coupling determined in temperature-dependent photoluminescence spectra indicate quantum-size effect. Our results demonstrate that ZnO/Mg_<i>x</i>Zn_1–<i>x</i>O MQWs integrated on Si have great potential in UV optoelectronic device applications