Current injection efficiency induced efficiency-droop in InGaN quantum well light-emitting diodes

Current injection efficiency and its impact on efficiency-droop in InGaN single quantum well (QW) based light-emitting diodes (LEDs) are investigated. The analysis is based on current continuity relation for drift and diffusion carrier transport across the QW-barrier system. A self-consistent 6-band k · p method is used to calculate the band structure for InGaN QW. The analysis indicates that the internal quantum efficiency in the conventional 24-Å In0.28Ga0.72N–GaN QW structure reaches its peak at low injection current density and reduces gradually with further increase in current due to the large carrier thermionic emission. Structures combining 24-Å In0.28Ga0.72N QW with 15-Å Al0.1Ga0.9N barriers show slight reduction in quenching of the injection efficiency as current density increases. The use of 15-Å Al0.83In0.17N barriers shows significant reduction in efficiency-droop (10% reduction of the internal quantum efficiency at current density of 620 A/cm2). Thus, InGaN QWs employing thin layers of larger bandgap AlInN barriers suppress the efficiency-droop phenomenon significantly.