Study of luminous efficiency droop behavior at high current density for InGaN/GaN multiple-quantum wells light emitting diodes
Date Issued
2008
Date
2008
Author(s)
Lai, Yu-Hung
Abstract
In recent thesis, InGaN/GaN-based light-emitting diodes (LEDs) with various well thicknesses are investigated. The so-called efficiency droop behavior is the reduction of LED’s emitting efficiencies at higher current densities. In this research, to understand the efficiency droop phenomenon both experiment and simulation are performed. Photoluminescence experimental results showed that thinner well structure has higher relative internal quantum efficiency. This is attributed to the smaller electron-hole charge separation induced by internal field with thinner wells. Electroluminescence experimental results showed that thicker well structure behaves less efficiency droop. On the other hand, thinner well structure has significant efficiency reduction at high current densities. It is assumed that Auger recombination as carrier concentration raised and carrier overflow at higher current densities are the dominant mechanism for the reduction of efficiency. However, according to simulation results, the efficiency droop behavior from low to high current density is contributed by Auger recombination first, then by carrier overflow at higher current density. The more optical characteristic in each structure will be further discussed.
Subjects
gallium nitride； quantum well； quantum-confined Stark effect (QCSE)； light-emitting diode (LED)； efficiency droop
Type
thesis
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