Phase Transition and Band Structure Tuned by Strains in Al$_{1/2}$Ga$_{1/2}$N Alloy of Complex Structure
Li-Xia Qin1**, Rong-Li Jiang2
1Department of Physics and College of Chemical Engineering, China University of Mining and Technology, Xuzhou 221116 2College of Chemical Engineering, China University of Mining and Technology, Xuzhou 221116
Abstract：Phase transition and band structure tuned by uniaxial and biaxial strains are systematically investigated based on the density-functional theory for ordered Al$_{1/2}$Ga$_{1/2}$N alloys of complex structures. Although the structural transformations to graphite-like from wurtzite are energetically favorable for both types of strain, the phase transitions are different in nature: the second-order transition induced by uniaxial strain is jointly driven by the mechanical and dynamical instabilities and the first-order transition by biaxial strain only by the mechanical instability. The wurtzite phase always shows the direct band gap, while the band gap of the graphite-like phase is always indirect. Furthermore, the band gaps of the wurtzite phase can be reduced by both types of strain, while that of the graphite-like phase is enhanced by uniaxial strain and is suppressed by biaxial strain.
2016, Vol. 33 
