Efficiency Droop and Effective Active Volume in GaN-Based Light-Emitting Diodes Grown on Sapphire and Silicon Substrates

Abstract

We compared the efficiency droop of InGaN multiple-quantum-well (MQW) blue light-emitting diode (LED) structures grown on silicon(111) and c-plane sapphire substrates and analyzed the efficiency droop characteristics using the rate equation model with reduced effective active volume. The efficiency droop of the LED sample on silicon was observed to be reduced considerably compared with that of the identical LED sample on sapphire substrates. When the measured external quantum efficiency was fitted with the rate equation model, the effective active volume of the MQW on silicon was found to be ~1.45 times larger than that of the MQW on sapphire. The lower efficiency droop in the LED on silicon could be attributed to its larger effective active volume compared with the LED on sapphire. The simulation results showed that the effective active volume decreased as the internal electric fields increased, as a result of the reduced overlap of the electron and hole distribution inside the quantum well and the inhomogeneous carrier distribution in the MQWs. The difference in the internal electric field of the MQW between the LED on silicon and sapphire could be a major reason for the difference in the effective active volume, and consequently, the efficiency droop.

Carrier Recombination in Nitride-Based Light-Emitting Devices: Multiphonon Processes, Excited Defects, and Disordered Heterointerfaces

“…The complexities of charge carrier recombination processes in nitride-based lightemitting devices (LEDs) are crucial in understanding various related physical phenomena. These phenomena include the efficiency droop effect, characterized by a decrease in efficiency with increasing injection currents, a reduction in efficiency due to higher indium or aluminium content (known as the "green gap" issue), notably low efficiency levels of UV LEDs using AlGaN alloys, reversible degradation processes, the short lifespan of laser diodes, and the creation of defects under injection current [1][2][3][4][5][6][7][8][9][10].…”

High-Speed Light Signal Transmitters for Optical Communication Based on Ultraviolet Radiation

“…MQWs have been a significant area of research in recent years [3][4][5]. Optical communication systems transmit information through modulated optical signals from ultraviolet to infrared.…”