Comparative study on electronic and optical properties for composition-tunable GaAlAs and InGaAs nanowires from first-principles calculation

The electronic and optical properties of composition-tunable Ga1-xAlxAs and InyGa1-yAs nanowires are investigated and compared utilizing first-principle calculations based on density functional theory. In the established nanowire models, nine different compositions (x/y = 0, 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875, 1) are considered. The results show that increasing Al constituent can enhance the stability of Ga1-xAlxAs nanowires, while increasing In content in InyGa1-yAs nanowires results in an opposite trend. Among all nanowires, In0.75Ga0.25As nanowire exhibits the lowest work function. Interestingly, Ga1-xAlxAs nanowires with Al composition less than 0.5 are direct band gap materials, while increasing Al content to 0.5 or above will induce indirect band gap. All InyGa1-yAs nanowires are all direct band gaps. Moreover, with increasing Al and In component, the absorption peak, reflection peak and refractive index for Ga1-xAlxAs are all blue shifted while inversely those of InyGa1-yAs nanowires are all red shifted. All calculations lay important foundation for the design and preparation of Ga1-xAlxAs and InyGa1-yAs nanowires based optoelectronic devices.