Polarization-doped quantum wells with graded Al-composition for highly efficient deep ultraviolet light-emitting diodes

The efficiency performance of AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) suffers from the strong polarization effect in multiple quantum wells (MQWs). Here, we propose V-shaped QWs to improve the quantum efficiency of DUV LEDs. We numerically investigated the effect of QWs with graded Al-composition on the device performance of DUV LEDs. Simulation results show that the QWs with graded Al-composition can mitigate the detrimental factors of traditional QWs with flat Al-composition, such as tilted energy band and separation of carrier wave function. Furthermore, compared to the QWs with linearly decreased or increased Al-composition along the growth direction, the V-shaped QWs can simultaneously alleviate the slope of valance and conduction band and obtain the better carrier confinement ability. Therefore, the DUV LED with V-shaped QWs exhibits a better optical performance.