Phase Transition and Band Structure Tuned by Strains in Al_(1/2)Ga_(1/2)N Alloy of Complex Structure

• 作 者: 秦丽霞 蒋荣立
• 机 构: Department of Physics and College of Chemical Engineering,China University of Mining and Technology,
• 出 处: Chinese Physics Letters
• 发表日期: 2016年07期
• 关键词: graphite systematically favorable dynamical jointly suppressed uniaxial instabil

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.

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 consequent 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. Future and 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.