Alleviated Asymmetry in Carrier Transport With V-Shaped Multiple Quantum Wells in AlGaN-Based DUV LEDs

Abstract

AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) still suffer from relatively low light output power (LOP) and poor external quantum efficiency (EQE) due to the severe electron leakage and hole-blocking effects. Electrons tend to accumulate in the last quantum well (LQW) and escape from the active region because of the weak confinement ability of the quantum barriers (QBs). Besides, the polarization-induced positive charges at the last QB (LQB)/p-type electron blocking layer (p-EBL) interface will attract electrons and consume holes for nonradiative recombination, leading to inadequate carrier concentration in the active region. In this article, we propose DUV LEDs with V-shaped multiple quantum wells (MQWs) to modulate the distribution of carriers in the active region. With the V-shaped MQWs, carriers are inclined to accumulate in the middle quantum well (QW) instead of the last one, and the polarization-induced electric field in the middle QW is also well alleviated, contributing to improved radiative recombination rates. Furthermore, the original positive sheet charges at the LQB/p-EBL interface are converted into negative ones, which is beneficial for suppressing electron overflow and increasing hole injection efficiency. Therefore, the EQE is remarkably improved by 48.1% at an injection current of 150 A/cm2. The V-shaped MQWs provide an effective solution to realize DUV LEDs with high performance.