Effects of indium mole fraction on the physical characteristics of magnetron sputtered In sub(x)Al sub(1-x)N films

In sub(x)Al sub(1 - x)N films with composition 0.25 less than or equal to x less than or equal to 0.86 were grown on p-type Si (111) substrates by using reactive magnetron co-sputtering technique in an ambient of argon and nitrogen at 200 degree C. X-ray diffraction results at x = 0.25 and x = 0.40 indicated the formation of nanostructured InAlN films along (101) plane with low diffraction intensities. However, by increasing the indium mole fraction 'x' from 0.40 to 0.86, crystallinity of the InAlN film was considerably improved along with a change in its preferred orientation towards the c-plane. Surface morphology analysis revealed an under-dense grains structure at x = 0.25, which was changed into a compact structure with increase of the 'x' value. Surface roughness of the films exhibited a decreasing trend with increase of the indium contents whereas the Raman spectroscopy analysis specified the existence of A sub(1) (LO) and E sub(2) (high) phonon modes in the films at x = 0.40 and x = 0.86. The Hall measurements indicated n-type nature of In sub(x)Al sub(1 - x)N film along with a decrease in its electrical resistivity with increase of the indium composition 'x'. The current-voltage (I-V) characteristics at x = 0.25 displayed Schottky behavior at the metal/film interface which was changed into the ohmic one with increase of indium mole fraction in the film.