Polarity tuning of crystalline AlN films utilizing trace oxygen involved sputtering and post-high-temperature annealing

The polarity tuning of AlN films via introducing a period of trace oxygen supply in the initial sputtering process was demonstrated. High-temperature annealing was further implemented to improve the crystal quality of AlN. High-quality pure N-polar AlN film could be achieved by sputtering with pure N2 gas. When trace oxygen was intentionally inputted in the sputtering chamber and its supply time surpassed 150 s, the AlN surface polarity transmitted to pure Al-polar. After optimization, the full widths at half of maximum of X-ray rocking curves for (0002)/(10-12) reflection were improved to 41.3/132.5 arcsec for N-polarity and 38.2/158.7 arcsec for Al-polarity.