Red & blue micro LED photoelectric characteristics analysis

• Main Authors: Chen, Shih-Yen, 陳詩硯
• Other Authors: Lin, Chien-Chung
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/t64365

碩士 === 國立交通大學 === 光電科技學程 === 107 === This thesis studied the photoelectric characteristics of the micro LEDs, light-emitting diodes with chip sizes down to the micron scale, and discussed the differences between the micro LEDs and the traditional ones. Firstly, blue and red micro LEDs with chip sizes of 10um x 10um, 30um x 30um and 50um x 50um were fabricated, and then the photoelectric properties of these micro LEDs were measured by integrating spheres, and the measured data were analyzed. In order to measure the light output without the influence of the soldering pad, each micro LED with vertical structure was fabricated, the electrode was made by plating ITO on top of the chip with its plating area larger than the light emitting area. The soldering pad was placed on the ITO film at the position out side the light output area. By utilizing the transparent and conductive characteristics of ITO film, this kind of soldering pad arrangement does not obstruct the grain luminescence and hence does not affect the photoelectric characteristics measurement. The measured data shows that both blue and red micro LEDs exhibit the same trend that the smaller the chip size the lower the voltage at the same current density.The analysis shows different trend on the external quantum efficiency. The smaller the chip size of blue micro LED the higher the external quantum efficiency. At the same current density of 20A/cm2, the external quantum efficiency of 10um x 10um blue micro LED is 9.45%, compare to that of 100um x 100um blue LED is only 5.13%. Contrary to blue micro LED, the smaller the chip size of red micro LED the lower the external quantum efficiency. The external quantum efficiency of 10um x 10um red micro LED is only 1.33%, while that of 100um x 100um red LED is 4.92% at the same current density of 20A/cm2.As the current density increases, the wavelength of all sized blue LEDs will first appear the phenomenon of blue-shift and then the red-shift, while the larger the chip size of blue LEDs the more obvious the red-shift. The wavelength of red LEDs is continuously red-shifted, the larger the chip size of red LEDs the more obvious the red-shift. The experiment successfully made the blue and red micro LEDs with chip size as small as 10um x 10um, and analyzed the photoelectric characteristics. It has taken a big step in the research of micro LEDs.