| Summary: | 碩士 === 國立交通大學 === 電子工程學系 電子研究所 === 102 === In this thesis, we use a model to investigate the influence of Shockley-Read-Hall recombination, radiative recombination, Auger recombination, effective volume, and leakage current on efficiency droop in blue light emitting diodes (LEDs). We find that increasing the ratio of radiative recombination to overall recombination rate, can improve the peak value of the external quantum efficiency (EQE) and alleviate the efficiency droop phenomenon. Besides, the decrease in the effective volume does not change the EQE peak value, but severely deteriorates the efficiency droop. We also find that a small effective volume may cause a significant leakage current at a low total current density.
We also study reasons for the difference in measured EQE curves between blue and green LEDs. We find that the efficiency droops more significantly for green LEDs than blue ones, due to a larger Auger coefficient and a smaller effective volume which results from indium aggregation or other factors causing more incomplete wave function overlap. Moreover, for both blue and green LEDs, the ratio of the leakage current to the total current is less than one percent in a normal operating current level. This indicates that the leakage current can be excluded from the origin of efficiency droop.
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