Optical second-harmonic generation in sputter-deposited AlN films

Results of a study of optical second-harmonic (SH) generation in AlN films deposited on borosilicate glass by reactive direct current magnetron sputtering are reported. As determined by x-ray diffraction (XRD). the films were highly c-axis oriented. The transmitted SH signal for film thickness ranging from 340 to 7800 Å was measured. The signal was consistent with the existence of a dead layer (in which no SH was generated) on the film surface with an effective thickness of ∼300 Å. A set of 7800-Å-thick films were deposited at substrate temperatures from ambient to T_s=400°C. For films deposited at 100°C or higher, minimal variation in the SH signal with T_s was found. Values of |d₃₃|=4 pm/V and |d₃₁|=0.04 pm/V, with d₃₃ and d₃₁ having the same sign, were obtained for T_s=400°C. The approximate tilt angle of the optic axis of the films with respect to the substrate surface normal was determined. XRD results showed that the tilt was due to a tilt of the crystallographic texture axis.