Crystal structures and stabilities of AlxGa1-xN and P-Type AlxGa1-xN with different Al compositions: A density functional study. (March 2020)

• Record Type: Journal Article
• Authors: Tang, Liu; Zhang, Hong; Yuan, Yinmei
• Is Part Of: Vacuum. Volume 173(2020)
• Publication Date: 2020-03
• Subjects: Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2020.109170
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: The crystal equilibrium structures, stabilities and electronic structures of Alx Ga1-x N and p-type Alx Ga1-x N with different Al compositions were investigated by the plane wave pseudo-potential method which is based on density functional theory. The calculation results show that the higher the Al composition in Alx Ga1-x N and Alx Ga1-x N:Mg, the more stable the structure, and the main factor influencing the stability is the type of atom rather than the position of the atom. By analyzing the electronic density of states, charge density difference and Mulliken overlap population, the bonding mechanism of M-N bond (M = Al, Ga or Mg) and their bond strength (Al–N > Ga–N > Mg–N) are obtained. Moreover, it was also found that an increase in the number of Al–N bonds has a "squeezing effect" on the Alx Ga1-x N and Alx Ga1-x N: Mg crystal and causes an increase in Ga–N and Mg–N bond energy. The higher the Al component, the better the stability is due to the increase of the number of Al–N bonds with strong bond energy and the increase of the bond energy of Ga–N and Mg–N bonds due to the "squeezing effect". More importantly, the essential reason was inferred for the difficulty in growing AlGaN single crystal films with high Al content and p-type doping. Highlights: The isomers of Alx Ga1-x N crystals with the identical Al composition has the same stability. The stability of Alx Ga1-x N and Alx Ga1-x N: Mg crystals with higher Al composition is superior. The rising number of Al–N bonds produces a "squeezing effect" on the crystal and leads to the strengthening of other bonds.