IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Electronics Wednesday Sessions
       Session EL-WeA

Paper EL-WeA5
Optical and Structural Characterization of GaN Films Grown by Molecular Beam Epitaxy on SiC Coated Si Substrates

Wednesday, October 31, 2001, 3:20 pm, Room 124

Session: Semiconductor Growth
Presenter: M. Lopez-Lopez, CINVESTAV-IPN, Mexico
Authors: M. Lopez-Lopez, CINVESTAV-IPN, Mexico
M. Cervantes-Contreras, CINVESTAV-IPN, Mexico
M. Melendez-Lira, CINVESTAV-IPN, Mexico
M. Tamura, CINVESTAV-IPN, Mexico
Correspondent: Click to Email
High-quality GaN layers are difficult to grow on Si substrates due to the large lattice mismatch (17%), and the problems associated to the growth of a polar material on a non-polar substrate. MBE growth of GaN directly on Si frequently results in films with a mixture of the stable hexagonal phase and the metastable cubic phase. Single-crystal cubic GaN films can be obtained by coating the Si substrates with a thin SiC layer.@footnote 1@ Here we present a study of the effects of the orientation of SiC-coated Si substrates on the MBE growth of GaN. The GaN layers were grown in a conventional MBE system with an RF activated nitrogen plasma source. (100)- and (111) oriented Si substrates were chemical treated in a HF solution, and then annealed in the MBE preparation chamber under a C@sub 2@H@sub 2@ partial pressure. This resulted in the formation of ~2.5 nm-thick SiC epitaxial layer. Transmission electron microscopy and x-ray diffraction results showed that the growth on SiC-coated Si(100) leads to cubic GaN films, the growth on SiC-coated Si(111) resulted in predominantly hexagonal GaN. 12K-photoluminescence spectroscopy (PL) of the films on (100) substrates showed an intense emission at ~3.1 eV associated to a donor-acceptor pair transition. However, the PL spectra of films on (111) substrates showed an additional peak at ~2.4 eV, which could be associated to crystal defects. 300K-photoreflectance (PR) spectra presented transitions at ~3.2 and ~3.4 eV for GaN on (100)- and (111) Si substrates, respectively. A quantitative analysis of the PR line spectra was carried out using the third-derivative function theory. We obtained band-gap energy values lower than those generally accepted. These red shifts could be associated to residual tensile strain in the epilayers due to the lattice mismatch and the difference in thermal expansion coefficients between GaN and the Si substrate. @FootnoteText@ @footnote 1@ Y. Hiroyama and M. Tamura: Jpn. J. Appl. Phys. 37 (1998) L630.