Controlling the polarity of ScAlN via formation of cation/anion vacancy

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Previously, we have confirmed that the addition of element such as Si or Ge could inverse the polarity of ScAlN from Al-polar to N-polar. However, addition of Carbon (C) could not inverse the polarization direction of ScAlN, which is suspected to be due to the presence of nitrogen vacancy (Vn). The role of Vn on polarity is confirmed in this fiscal year by addition of element that theoretically can generate nitrogen vacancy such as magnesium (Mg) or zinc (Zn). It was found that addition of Mg or addition of Zn into ScAlN yielded in thin films with Al-polarity, which means that addition of either element was unable to inverse the polarity of ScAlN from Al-polar to N-polar. Increase in concentration of Mg or Zn added into ScAlN was only resulted in a decrease in wurtzite phase stability which led to lower piezoelectric d33 response. These results further confirm that the presence of nitrogen vacancy could not induce polarity inversion in nitride. Also, our presentation in JSAP Spring meeting 2023 was also nominated to receive best poster award.