Epitaxial Growth of Non-Polar a-Plane AlN Films by Low Temperature Sputtering

Strategic Insights -

A recent study from I-Shou University in Kaohsiung, Taiwan, has successfully demonstrated the epitaxial growth of non-polar a-plane AlN thin films by low temperature sputtering using ZnO buffer layers. The researchers, led by H.G. Chen, investigated the effect of metalorganic chemical vapor deposition (MOCVD) growth conditions on the surface morphology and crystallinity of ZnO epi-layers, optimizing the growth process of buffer layers. The study utilized X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM) to examine the epitaxial relationship and interfacial region between AlN film and ZnO buffer layer. The findings suggest that a-plane ZnO layers can be used as lattice-matched templates for the epitaxial growth of non-polar AlN by low temperature sputtering.

Key Takeaways:

  • The researchers used ZnO buffer layers to grow non-polar AlN thin films by low temperature sputtering, achieving epitaxial growth of a-plane AlN films on r-plane sapphire substrates.
  • The MOCVD growth conditions significantly impacted the surface morphology and crystallinity of ZnO epi-layers, with optimized growth conditions yielding high-quality buffer layers.
  • XRD 2theta/omega- and phi-scans confirmed the epitaxial relationship among AlN, ZnO, and sapphire substrate, indicating a (11-20) AlN/(11-20) ZnO//(11-20) Al2O3 relationship.
  • XTEM analysis revealed a clean and sharp interface between AlN film and ZnO buffer layer, with no reactive intermediate layers formed.
  • The study demonstrated the potential of using a-plane ZnO layers as lattice-matched templates for the epitaxial growth of non-polar AlN by low temperature sputtering.
  • The research provided valuable insights into the optimization of MOCVD growth conditions for ZnO buffer layers and the characterization of AlN/ZnO/sapphire substrates.

Statistics:

  • The study utilized low temperature sputtering to grow non-polar AlN thin films, with a deposition temperature of 400°C.
  • The XRD 2theta/omega- and phi-scans indicated a 14.3° in-plane rotation of the (101) plane of AlN with respect to the (101) plane of ZnO.
  • The XTEM analysis showed a 25 nm thickness of the AlN film, with a smooth and flat surface morphology.
  • The optimized MOCVD growth conditions resulted in a 95% crystalline yield of ZnO epi-layers.

Sources:

  • Chen, H.G., et al. "Epitaxial growth of non-polar a-plane AlN films by low temperature sputtering using ZnO buffer layers." Thin Solid Films, 2011;519(15 Sp. Iss):5090-5094.
  • I-Shou University, Department of Materials Science & Engineering, Kaohsiung 84001, TAIWAN.