Well and Polarization Effects on Carrier Distribution and Interband Transitions in NUV Light-Emitting Diodes

The illumination efficiency and the relevant physical mechanism of near-ultraviolet (NUV) AlGaN-based light-emitting diodes (LEDs) are investigated numerically. In particular, the interrelationship of quantum well (QW) thickness and degree of polarization, and the relevant influence on the light output power of NUV LEDs are systematically studied. Simulation results indicate that the use of wider QWs with less polarization field is beneficial in suppressing the Auger recombination by reducing the carrier density. However, the structure with wider QWs suffers from severer spatial separation of electron and hole wave functions within the QW, which is more sensitive to the degree of polarization in its optical performance. To resolve this problem, the quaternary Al_0.1In_0.05Ga_0.85N is proposed as the material of quantum barriers in wide QWs, in which the polarization mismatch between the QW and the barrier is reduced and the relevant quantum-confined Stark effect is relieved consequently.