Investigation on Characteristics of Blue Light-Emitting Diode Array and Thermal Effect of Blue Light-Emitting Transistors

• Main Authors: I-Chen Tseng, 曾怡蓁
• Other Authors: Chao-Hsin Wu
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/zg48hs

碩士 === 國立臺灣大學 === 光電工程學研究所 === 106 === The core of this paper is the research and discussion of the characteristics of blue light-emitting diode arrays, including analyzed the effect of the array numbers on the light intensity, modulation bandwidth, equivalent circuit model and data transmission. At present, there are many studies devoted to the development of high-speed blue light diodes, starting from epitaxy, geometry, and manufacturing processes. Pursuing higher modulation speeds to be applied to visible light communication. Generally speaking, the higher modulation speed can be achieved by scaling down the device area. Because the small size component can withstand higher current density and lower junction temperature to achieve higher modulation width. However, reducing the component area will sacrifice light intensity. As a component of the light source for visible light communication, it must have both modulation speed and illumination function. Therefore, how to develop a high-speed blue LED and simultaneously have a lighting function is a major problem that must be overcome. In this paper, by integrating the micro-light emitting diodes into a parallel array, the effects of the number of arrays on the luminous power and the modulation speed are discussed. We have obtained a linearly increase in the light intensity as the array number increases. The modulation bandwidth of the different arrays behave the same at the same current density, which means the array configurations can enhance the optical power while not lose the modulation speed. We further measure the data rate characteristics of different arrays, and find that the device with more array numbers can exhibit better performance in data transmission characteristics. In summary, the light intensity can be enhanced and better data transfer quality can be obtained through the array structures. In addition, after our lab successfully manufacture the first blue quantum well (QW) luminescent transistor, and present its basic optoelectronic characteristics and spectrum, we further investigate the thermal effects of blue luminescent transistors. The current gain of the traditional heterogeneous bipolar becomes smaller as the temperature rises. When the temperature rises, the difference between the base and emitter junctions becomes smaller, resulting in more reflow carriers and smaller current gain. Different from traditional heterogeneous bipolar, the thermal effect on LETs is very different. Because the capture and escape mechanism in the QW, the carrier escape time equation is inversely proportional to the temperature, that is, the temperature rises, and the carrier escape time is shorter. The escaped carrier will run to the collector to form a collector current, so that the current gain of the light-emitting transistor becomes larger as the temperature increases. Through this mechanism, the light-emitting transistor can be applied to the temperature sensor. What’s more, the blue light-emitting transistors are more easily detected than GaAs-based (infrared) light-emitting transistors. As a result, blue LET is more suitable for thermal sensor application because they are visible light. Furthermore, we use the carrier control model to learn more about the thermal effect on the LET. By solving the boundary conditions and bringing in the parameters of the experimental results, we can obtain the distribution of carriers in the base region under different temperature. With the above characteristics, blue light-emitting transistors will be the key components for future visible light communication and optical interconnection.