Design of type-II MgxZn1-xO:N/ZnO superlattices for UV photodetector applications

Electronic structures of N-doped and undoped Mg0.25Zn0.75O/ZnO superlattices (SLs) were investigated by using a first-principles calculation. The partial charge density profiles show that electron and hole states are separated into ZnO and N-doped Mg0.25Zn0.75O layers. This property is further confirmed by the calculations of layer-projected density of states, which demonstrate that a type II band alignment is produced in an N-doped Mg0.25Zn0.75O/ZnO SL. The bandgap of the type II band alignment was evaluated to be adjusted through different MgO mole fractions. The results suggest the N-doped MgxZn1-x/ZnO SLs to apply to ultraviolet photodetectors with different cut-off wavelengths.