| Summary: | 碩士 === 南臺科技大學 === 電子工程系 === 103 === In this research, nitride-based light-emitting diodes (LEDs) with different Mg-doped in the quantum barrier were investigated. The investigation of experiment different Mg-doped in the last barrier have significant influence on the forward voltage, leakage current, electrostatic discharge, light output power, power efficiency, carrier distribution, radiative recombination rate and temperature effect.
The forward voltages of LED I, LEDII, LEDIII and LEDIV under an injection current of 120 mA were 3.31V, 3.22V, 3.19V and 3.18V, respectively. Such a result indicates that the electrical properties of nitride-based LEDs can be significantly improved by doping Mg in the last quantum barrier which affects the valance band barrier height for the p-EBL and helps to increase the hole injection. We can be observed that the light output power (LOP) increased with increasing injection current. Under an injection current of 120 mA, it was found that the output powers of LED I, II, III and IV were 89.67mW, 92.80mW, 91.31mW and 86.64mW, respectively. And, the droop ratio of LED I, II, III and IV were 31.54%, 32.62%, 32.32% and 31.20%, respectively. As the result, it can be attributed to the increase of hole injection efficiency and the reduction of the electron leakage when the effective barrier height at LB/EBL interface is increased. Thus, these two mechanisms were improved so that the radiative recombination rate in the active region markedly was enhanced. However, high concentration of Mg involved generation of deep recombination centers and compensating centers that strongly restrict conductivity and photoconductivity. In addition, the high Mg-doping concentration region in close vicinity to the InGaN QWs tended to increase non-radiative recombination rates.
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