Fig. 1. (Color online) (a) XRD spectra of Ga-assisted AlN films under varying TMGa flow rates respectively, (b) EDS spectra of Ga-assisted AlN sample S5.

Fig. 2. (Color online) (a)−(e) The cross-sectional SEM images of Ga-assisted AlN films grown under different TMGa flow rates and corresponding 5 × 5 μm² AFM images, (f) Ga-assisted AlN growth rates as a function of Ga proportion.

Fig. 3. (a)−(f) SEM images of Ga-assisted AlN films grown with different Ga flow rates.

Fig. 4. (Color online) The results of the Raman spectroscopy measurement.

Fig. 5. SEM images of AlN nucleation morphology (a) without TMGa and (b) with 80% TMGa.

Fig. 6. (Color online) (a−c) Schematic diagram of Ga-assisted AlN growth, (d−f) W/O Ga-assisted AlN growth.

Fig. 7. (Color online) (a, b) X-ray rocking curves of AlN (002) and (102) planes of samples S1−S5, (c) the variation curves of the full width at FWHM of AlN (002) and (102) planes of samples S1−S5, (d) AlN growth rate and growth temperature as function of Ga proportion.

Fig. 8. (Color online) FWHM values of AlN (002) (a) and (102) (b) planes, surface morphology (c) and growth thickness (d) of Sample S6.