On the crystalline structure, stoichiometry and band gap of InN thin films

• Published in: Applied physics letters 2005-02, Vol.86 (7), p.071910-071910-3
• Main Authors: Yu, K. M., Liliental-Weber, Z., Walukiewicz, W., Shan, W., Ager, J. W., Li, S. X., Jones, R. E., Haller, E. E., Lu, Hai, Schaff, William J.
• Format: Article
• Language: English
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.1861513

Detailed transmission electron microscopy, x-ray diffraction (XRD), and optical characterization of a variety of InN thin films grown by molecular-beam epitaxy under both optimized and nonoptimized conditions is reported. Optical characterization by absorption and photoluminescence confirms that the bandgap of single-crystalline and polycrystalline wurtzite InN is 0.70 ± 0.05 eV . Films grown under optimized conditions with an AlN nucleation layer and a GaN buffer layer are stoichiometric, single-crystalline wurtzite structure with dislocation densities not exceeding mid - 10 10 cm − 2 . Nonoptimal films can be polycrystalline and display an XRD diffraction feature at 2 θ ≈ 33 ° ; this feature has been attributed by others to the presence of metallic In clusters. Careful indexing of wide-angle XRD scans and selected area diffraction patterns shows that this peak is in fact due to the presence of polycrystalline InN grains; no evidence of metallic In clusters was found in any of the studied samples.