不同转移工艺制备的垂直结构Si衬底GaN基LED光衰研究

发布时间：2018-04-21 06:50

本文选题：Si衬底 + 转移　；参考：《南昌大学》2015年硕士论文

【摘要】：近年来,半导体照明得到了突飞猛进的发展,GaN基材料尤其是InGaN/GaN LED在材料生长及LED的制备等方面已日趋成熟。现如今,LED显示,背光和照明市场都已启动,但距离LED灯全面进入家庭照明还有很长的一段路要走,还需要进一步提高其光电性能和降低价格。Si以其低成本,大尺寸,高质量,导电,导热等优点,在半导体照明行业中异军突起。近年来,本实验室已经研制出了高性能Si衬底GaN基LED并实现产业化,打破了原来的LED市场格局。但Si衬底也存在一些缺点,即GaN材料之间存在着巨大的晶格失配和热失配。这使得Si上生长的GaN材料中存在着较大的应力,进而影响器件的光电性能。因此Si衬底GaN基LED外延材料生长和器件的制备还有一些问题亟待研究。本论文利用两种不同的转移工艺而获得两组垂直结构的GaN基LED芯片,即一次转移和三次转移工艺。一次转移工艺就是将原生衬底上的GaN薄膜上粘接金属层然后衬底转移,三次转移工艺是将原生衬底上的GaN外延薄膜粘接在一种柔性材料上然后去除Si衬底,再将其另一面粘接在另一种柔性材料上,最后在去除第二次引人的柔性材料并用共晶将GaN转移至另一Si基板上。本文对这两组芯片进行研究,分析应力分布状态对LED光电性能的影响。主要获得以下研究成果:1用750mA的正向电流对两组芯片进行24小时,168小时加速老化,老化后发现三次转移的芯片相比于一次转移的芯片光衰更大。通过分析,发现光衰的主要来源于光提取效率的下降。2通过XRD对两组芯片进行扫描,分析发现三次转移芯片的平整度不够好。通过台阶仪测试,发现了三次转移芯片的弯曲度相比于一次转移芯片的确实大很多。利用拉曼谱测芯片的应力分布,发现三次转移芯片应力分布均匀,而一次转移芯片应力分布均匀。利用电子扫描显微镜扫描芯片的截面,发现三次转移芯片在共晶界面出现缝隙。3本论文研究发现,三次转移工艺由于引人了柔性转移步骤,GaN薄膜的张应力能得到彻底释放,但应力释放的过程中薄膜会发生严一定的弯曲形变,导致共晶粘接时,界面不平粘接强度降低,从而引起老化时界面反射率衰退,出现光衰。
[Abstract]:In recent years, semiconductor lighting has been developed by leaps and bounds. Especially InGaN/GaN LED has become more and more mature in material growth and LED preparation. Today, LED shows that the market for backlight and lighting has started, but there is still a long way to go before LED lights can fully enter home lighting, and further improvements in its photoelectric performance and lower price. Si are needed for its low cost, large size and high quality. Electric conduction, heat conduction and other advantages, in the semiconductor lighting industry springing up. In recent years, GaN based LED on high performance Si substrates has been developed and industrialized in our laboratory, which breaks the original LED market pattern. However, there are some disadvantages in Si substrate, that is, there is a huge lattice mismatch and thermal mismatch between GaN materials. As a result, there is a large stress in the GaN material grown on Si, which affects the photoelectric performance of the device. Therefore, there are still some problems in Si substrate GaN based LED epitaxial material growth and device fabrication. In this paper, two groups of vertical GaN based LED chips are obtained by using two different transfer processes, namely, primary transfer and tertiary transfer. The first transfer process is the bonding of the GaN film on the primary substrate to the metal layer and then the transfer of the substrate. The third transfer process is that the GaN epitaxial film on the primary substrate is bonded to a flexible material and then removed from the Si substrate. Then the other side is bonded to another kind of flexible material, and finally the second attractive flexible material is removed and the GaN is transferred to another Si substrate by eutectic. In this paper, the effects of stress distribution on the optoelectronic properties of LED are studied. The following research results were obtained: 1: 1 accelerated aging of the two groups of chips with forward current of 750mA for 24 hours or 168 hours. After aging, it was found that the chip with three times transfer had greater light decay than the chip with one transfer. Through analysis, it is found that the main source of light decay is the decline of optical extraction efficiency. 2. Scanning the two groups of chips through XRD. The analysis shows that the smoothness of the triple transfer chip is not good enough. It is found that the bending degree of the triple transfer chip is much larger than that of the single transfer chip. Using Raman spectroscopy to measure the stress distribution of the chip, it is found that the stress distribution of the triple transfer chip is uniform, while the stress distribution of the first transfer chip is uniform. By using the cross section of the scanning electron microscope scanning chip, it is found that the third transfer chip has a gap of .3 at the eutectic interface. In this paper, it is found that the tensile stress of the gan film can be completely released by the third transfer process because of the inducement of the flexible transfer step. However, during stress release, the film will be bent and deformed to a certain degree, which will lead to the decrease of the interfacial uneven bonding strength during eutectic bonding, which will result in the decay of the interface reflectivity and the light decay during the aging process.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ133.51;TN312.8

【参考文献】