We have investigated the structural properties of CrN layers grown on (0001) Al2O3 substrates by molecular-beam epitaxy. The CrN layers of high-crystal quality are obtained at a low growth temperature of 500 °C. X-ray diffraction studies indicate that the CrN layers grow along the 〈111〉 direction with a cubic structure. In-situ reflection high-energy electron diffraction investigations clarify that the CrN layers have the following epitaxy relationship with the Al2O3 substrates: 〈121〉 of (111) cubic CrN // 〈11-20〉 of (0001) corundum Al2O3 and 〈101〉 of (111) cubic CrN // 〈1-100〉 of (0001) corundum Al2O3. Based on the above results, the mismatch of the in-plane lattice spacing between the CrN layers and the Al2O3 substrates is evaluated to be around 6.6%. When the CrN layers are used as the buffer layers for GaN growth, the GaN layers grown on the CrN layers show well-resolved excitonic emission lines in the photoluminescence spectra, whereas the GaN layers grown without the CrN layers exhibit a broad near-band-edge emission. It is suggested that CrN buffers are effective in relieving the lattice mismatch between Al2O 3 substrates and GaN layers.
|Number of pages
|Journal of the Korean Physical Society
|Published - 2006 Sept
- Molecular-beam epitaxy