Manipulation of band structures in wurtzite and zinc-blende GaAs/InAs-core-shell nanowires

Using first principles calculation based on density-functional theory, we adopted internal and external two mechanisms to manipulate the band structures of wurtzite and zinc-blende GaAs/InAs-core-shell nanowires (NWs) along the [0001] and [111] directions, respectively. Variational geometry size and chemical component are the internal approaches to tune the band structures. The band gaps are nonlinear composition dependence for the core-shell NWs with fixed diameter and linear composition dependence for the NWs with fixed core. Using external uniaxial strain is another alternative approach. We found that the relative band gap decreases evidently with tensile strain, while it gradually increases with increasing compressive strain. The higher the ratio of GaAs composition in the core-shell NWs, the larger the variations of the relative energy. More interestingly, in wurtzite core-shell NWs, we found a critical reflection point, which results from the two competition states between bonding and anti-bonding. Compared with the wurtzite pure GaAs NWs, the reflection point of GaAs/InAs-core-shell NWs appears in a larger compressive strain.