Comparison of the Material Quality of AlInN (x-0-0.50) Films Deposited on Si(100) and Si(111) at Low Temperature by Reactive RF Sputtering.

AlInN ternary semiconductors have attracted much interest for application in photovoltaic devices. Here, we compare the material quality of AlInN layers deposited on Si with different crystallographic orientations, (100) and (111), via radio-frequency (RF) sputtering. To modulate their Al content, the Al RF power was varied from 0 to 225 W, whereas the In RF power and deposition temperature were fixed at 30 W and 300 °C, respectively. X-ray diffraction measurements reveal a c-axis-oriented wurtzite structure with no phase separation regardless of the Al content (x = 0-0.50), which increases with the Al power supply. The surface morphology of the AlInN layers improves with increasing Al content (the root-mean-square roughness decreases from ≈12 to 2.5 nm), and it is similar for samples grown on both Si substrates. The amorphous layer (~2.5 nm thick) found at the interface with the substrates explains the weak influence of their orientation on the properties of the AlInN films. Simultaneously grown AlInN-on-sapphire samples point to a residual n-type carrier concentration in the 10-10 cm range. The optical band gap energy of these layers evolves from 1.75 to 2.56 eV with the increase in the Al. PL measurements of AlInN show a blue shift in the peak emission when adding the Al, as expected. We also observe an increase in the FWHM of the main peak and a decrease in the integrated emission with the Al content in room-temperature PL measurements. In general, the material quality of the AlInN films on Si is similar for both crystallographic orientations.