Structural and optical characterization of AlN films grown by pulsed laser deposition

Abstract

AlN thin films were prepared on p-type Si(1 0 0) substrates heated at 800 °C by pulsed laser ablation of AlN targets using an UV KrF* ( λ = 248 nm, τ FWHM ≤ 10 ns) excimer laser. We report herewith new results in depositing AlN films from AlN targets and their characterization by X-ray diffraction (XRD), along with Fourier transform infrared (FTIR) investigations in reflection and spectroscopic ellipsometry data. The X-ray investigations confirm the formation of polycrystalline AlN films. We observed the complete absence of the Al line in the XRD spectra. The gradual decomposition of the AlN target in the zones beneath and around the crater, induced by nanosecond multipulse laser irradiation, was compensated by a low-pressure N 2 flux (0.1–10 Pa) during deposition. The reflection IR spectra display features characteristic to LO phonons in AlN. Ellipsometric measurements evidenced a refractive index of 2.00 and an extinction coefficient of 0.0001 for AlN films with a thickness of about 100 nm.