The band-gap energy and band-gap bowing parameter of the wurtzite AlGaN alloys are investigated numerically with the CASTEP simulation program. The simulation results suggest that the unstrained band-gap bowing parameter of the wurtzite AlGaN alloys is b = 0.353 ±0.024 eV. The simulation results also show that the width of the AlxGa1-xN top valence band at the Γ point decreases when the aluminum composition increases and has a value of 7.331 eV for the GaN (x=0) and 6.132 eV for the AlN (x=1).
