Effect of pressure and mechanical stress on the electronic properties of AlN and GaN

• Published in: Physics of the solid state 2011-04, Vol.53 (4), p.679-688
• Main Authors: Brudnyi, V. N., Kosobutsky, A. V., Kolin, N. G.
• Format: Article
• Language: English
• Subjects: Aluminum compounds; Analysis; Liquors; Physics; Physics and Astronomy; Rock-salt; Semiconductors; Solid State Physics
• ISSN: 1063-7834; 1090-6460
• DOI: 10.1134/S1063783411040093

The fundamental properties of the AlN and GaN compounds with a wurtzite structure under external hydrostatic pressure, uniaxial mechanical stress σ ⊥ along the hexagonal axis, and biaxial mechanical stress σ ⊥ in the basal plane of the unit cell have been considered in terms of first-principles calculations in the frame-work of the density functional theory. The pressures of the phase transitions from the structures of wurtzite and zinc blende to the structure of rock salt have been obtained. The behavior of the structural parameters, interband transitions, and positions of the charge neutrality level has been investigated. The calculated pressure coefficients of the band gap are as follows: ∂E g / ∂p = 40.9 meV/GPa, − ∂E g / ∂σ | = −4.2 meV/GPa, and − ∂E g / ∂σ ⊥ = 45.2 meV/GPa for AlN and ∂E g / ∂p = 33.0 meV/GPa, − ∂E g / ∂σ | = 23.6 meV/GPa, and − ∂E g / ∂σ ⊥ = 9.6 meV/GPa for GaN. The pressure coefficients of the charge neutrality level in almost all cases are substantially smaller than the corresponding values obtained for the band gap E g .