Exploring Al composition and diameter effect on Al_xGa_1-xAs nanowire photocathodes via first-principles calculations with DFT+U method

Abstract

Utilizing first-principles calculations with DFT+U method, the structural, electronic and optical behaviors of AlxGa1-xAs nanowire photocathodes modulated by Al composition and diameter are systematically investigated. The findings reveal that the structural stability of AlxGa1-xAs nanowires is progressively enhanced as either the Al composition or the wire diameter increases. Additionally, the charge transfer in nanowires induced by altering the Al composition is significantly greater than that caused by varying wire diameter. Wurtzite AlxGa1-xAs nanowire is a direct bandgap material. Moreover, the continuously reduced bandgap resulting from an increase in diameter confirms the size effect of the nanowire. In addition, the introduction of DFT+U method presents an accurate theoretical bandgap with higher efficiency. The error of the bandgap between predication and experimental results is less than 4% in the case of bulk AlxGa1-xAs. The optical property of AlxGa1-xAs nanowire is more susceptible to the influence of wire diameter compared to that of Al composition. Furthermore, the optical absorption spectrums exhibit a slight blueshift and a redshift with increasing Al composition and wire diameter, respectively. This study is anticipated to provide theoretical support for the design of optoelectronic devices based on AlxGa1-xAs nanowires.