Molecular beam epitaxial growth of GaN thin film on Si substrate with InN as interlayer

Low-temperature interlayer InN was used to fabricate GaN thin film on Si (1 1 1) substrate by molecular beam epitaxy method. Surface scanning electron microscopy image shows a uniform polycrystalline structure. Transmission electron microscopy and high-angle annular detector dark-field scanning transmission electron microscopy images indicate column GaN crystal microstructure with the diameter between 100 and 150 nm. Air-gap structure is formed between the high-temperature GaN film and the underlying buffer layer. Photoluminescence measurement shows a small peak of 357 nm at room temperature and an increase of peak intensity about 40 times at temperature 8 K. Room temperature Raman spectra of the GaN column crystals shows narrow full-width at half-maximum of 2 cm−1 and E2 mode peak line of 565.9 cm−1. A shift of 1.1 cm−1 from the intrinsic position may suggest relaxed residual strain of the GaN column crystals. The liquid In metal derived from the decomposed InN interlayer diffuses into the GaN buffer layer and high-temperature GaN thin film, forming InGaN layer. The application of InN as interlayer offers another effective way for the heteroepitaxial growth of GaN thin film on Si substrate.