High-efficiency InGaN blue LEDs with reduced positive sheet polarization

Abstract

The formation of positive sheet polarization charges at the interface of the last quantum barrier (QB) and the conventional p -type electron-blocking layer (EBL) creates significant band bending, leading to severe electron leakage and poor hole injection in III-nitride light-emitting diodes. We report that the positive sheet polarization charges are mitigated by employing a lattice matched AlGaN last QB. Electron leakage is dramatically reduced due to the increased effective conduction band height at the last QB and EBL. Furthermore, it favors hole injection into the active region due to the reduced effective valance band height for EBL.

Recent Research on Indium-Gallium-Nitride-Based Light-Emitting Diodes: Growth Conditions and External Quantum Efficiency

“…Velpula et al [148] indicated that the main reasons for the efficiency droop in LEDs are a large overflow of electrons from the active region into the active region and insufficient hole injection into the active region. Previous studies addressed this problem by introducing p-type AlGaN as an electron-blocking layer (EBL) to prevent electron leakage [42,149].…”

“…Moreover, the majority of charge carriers are likely confined and undergo radioactive recombination in the last quantum well just prior to the last QB (quantum barrier) of III-nitride-based multi-QW LEDs [154]. Velpula et al [148] utilized a novel AlGaN QB as a lattice-matched EBL used instead of a conventional GaN QB. The positive sheet charges at the last QB/EBL can be eliminated due to lattice-matched conditions at this interface.…”

Highly Stable White Light Emission from III-Nitride Nanowire LEDs Utilizing Nanostructured Alumina-Doped Mn4+ and Mg2+

“…Nanostructured III-nitride materials have attracted significant attention due to their great potential applications in micro-displays, conformable light sources, and augment/virtual reality technology. The light-emitting diodes (LEDs) that could emit different wavelengths from ultraviolet (UV), visible light, and infrared (IR) by controlling the In, Ga, and Al composition in In­(Al)­GaN materials are intensively investigated. − However, the fabrication of high-efficiency full-color LEDs, especially at long wavelengths (green and red light), remains a challenge that hinders the commercial availability of micro-displays. − In addition, luminous efficacy of the LEDs can attain 50 to 70% of the theoretical maximum . More than 30% of the energy is converted into heat which reduces the LED luminescent efficacy and lifetime.…”