初始应力对垂直结构GaN基LED光电性能影响的研究
发布时间：2019-01-08 18:47
【摘要】：GaN基LED作为照明光源既节能又环保,开启了人类照明的新时代,已经与人们的生活息息相关,因此2014年诺贝尔物理奖授予了GaN基LED的相关研究成果。目前,商品化的GaN基LED按外延衬底划分共有三条技术路线,分别是:碳化硅(SiC)、蓝宝石(Al2O3)及硅(Si)衬底技术路线.蓝宝石衬底LED市场份额最大,碳化硅衬底LED的市场占有率居中,硅衬底LED尽管市场占有率最小,但它的市场份额正在逐渐扩大且应用越来越广泛。尽管硅衬底技术路线具有一定局限性,人们还不清楚它将来是否会成为主流技术,但由于它具有诸多显著优点,目前已经成为LED领域的一大研究热点。硅衬底会吸收可见光以及硅衬底上外延的GaN基LED薄膜存在巨大的张应力,因此实用化的硅衬底LED均是采用邦定和湿法腐蚀相结合的技术将GaN基LED薄膜从外延衬底剥离转移到新的支撑基板上做成垂直结构的芯片。硅衬底GaN基LED薄膜存在巨大的外延张应力,在剥离转移到新基板后应力会得到一定程度的释放已有报道,然而,是否可以将硅衬底GaN基LED薄膜应力先完全释放后再邦定到支撑基板上做成垂直结构的芯片以及其光电性能是否会得到改善目前还没有报道。尽管三条技术路线的垂直结构LED均已实现商品化并获得了广泛应用,而且转移到新基板后应力的微小变化就会对GaN基LED的光电性能产生明显影响,然而同种衬底上相同结构的LED薄膜在转移到新的支撑基板时应该处于怎样的初始应力状态才能使其光电性能发挥到最佳目前还是研究空白。本文将外延结构相同的GaN基LED薄膜分别直接邦定和应力释放后再邦定到新的支撑基板上,获得了多种初始应力不同的垂直结构LED芯片,并对其光电性能进行了研究。1、当LED薄膜用有机柔性粘结层与基板粘结在一起,去除硅衬底后,LED薄膜所受来自于硅衬底的张应力基本会被完全释放。2、直接邦定和释放应力后再邦定的芯片其LED薄膜的张应力均会得到释放,其中释放应力后再邦定获得的芯片其张应力释放较为彻底,而直接邦定得到的芯片其张应力释放较小。3、在制备Si衬底垂直结构GaN基LED芯片的过程中,直接邦定的芯片其LED薄膜所受张应力状态会逐渐减小,而释放应力后再邦定的芯片刚好相反。4、垂直结构LED芯片的发光性能不仅仅会受LED薄膜初始应力的影响,而且还会受LED薄膜和支撑基板之间金属邦定层的影响。5、释放应力再邦定的芯片尽管阱层受到的压应力大于直接邦定的芯片,然而通过EQE归一化处理后,四种芯片的电流Droop效应相同。
[Abstract]:GaN based LED, as a lighting source, is not only energy saving and environmental protection, but also opens a new era of human lighting, which is closely related to people's lives. Therefore, the 2014 Nobel Prize in Physics has been awarded to the related research results of GaN based LED. At present, the commercial GaN based LED is divided into three technical routes according to the epitaxial substrate, namely, silicon carbide (SiC), sapphire (Al2O3) and silicon (Si) substrate. The market share of sapphire substrate LED is the largest, and silicon carbide substrate LED has the middle market share. Although silicon substrate LED has the smallest market share, its market share is gradually expanding and being used more and more widely. Although the technology route of silicon substrate has some limitations and it is not clear whether it will become the mainstream technology in the future, it has become a research hotspot in the field of LED because of its many outstanding advantages. The silicon substrate absorbs visible light and there is a great tensile stress on the epitaxial GaN based LED film on the silicon substrate. Therefore, the practical silicon substrates LED are chips with vertical structure from epitaxial substrates to new support substrates, which are transferred from epitaxial substrates to new support substrates by using the technology of bonding and wet etching. There is a huge epitaxial tensile stress in GaN LED films on silicon substrates. It has been reported that the stress will be released to some extent after peeling and transferring to new substrates. Whether the stress of GaN based LED film on silicon substrate can be completely released and then bonded onto the supporting substrate to form a vertical structure chip and whether its photoelectric performance will be improved has not been reported. Although the vertical structure LED of the three technical routes has been commercialized and widely used, and the slight change of the stress after transferring to the new substrate will have a significant effect on the optoelectronic properties of the GaN based LED. However, the initial stress state of the LED thin films with the same structure on the same substrate is still blank. In this paper, GaN based LED thin films with the same epitaxial structure are directly bonded and released respectively to a new supporting substrate. A variety of vertical structure LED chips with different initial stresses are obtained, and their optical and electrical properties are studied. When the LED film is bonded with the substrate by organic flexible bonding layer, the tensile stress of the LED film from the silicon substrate is basically completely released after the silicon substrate is removed. The tensile stress of the LED film will be released both directly and after releasing the stress, and the tensile stress of the chip after releasing the stress will be completely released. However, the tensile stress release of the direct bonding chip is relatively small. 3. In the process of fabricating the GaN based LED chip with vertical structure on the Si substrate, the tensile stress state of the LED film of the direct bonding chip will gradually decrease. The photoluminescence performance of vertical LED chip is not only affected by the initial stress of LED film, but also by the metal bonding between LED film and supporting substrate. Although the pressure stress in the well layer is higher than that in the directly bonded chip, the current Droop effect of the four chips is the same after EQE normalization.
【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】：TN312.8
本文编号：2404986
[Abstract]:GaN based LED, as a lighting source, is not only energy saving and environmental protection, but also opens a new era of human lighting, which is closely related to people's lives. Therefore, the 2014 Nobel Prize in Physics has been awarded to the related research results of GaN based LED. At present, the commercial GaN based LED is divided into three technical routes according to the epitaxial substrate, namely, silicon carbide (SiC), sapphire (Al2O3) and silicon (Si) substrate. The market share of sapphire substrate LED is the largest, and silicon carbide substrate LED has the middle market share. Although silicon substrate LED has the smallest market share, its market share is gradually expanding and being used more and more widely. Although the technology route of silicon substrate has some limitations and it is not clear whether it will become the mainstream technology in the future, it has become a research hotspot in the field of LED because of its many outstanding advantages. The silicon substrate absorbs visible light and there is a great tensile stress on the epitaxial GaN based LED film on the silicon substrate. Therefore, the practical silicon substrates LED are chips with vertical structure from epitaxial substrates to new support substrates, which are transferred from epitaxial substrates to new support substrates by using the technology of bonding and wet etching. There is a huge epitaxial tensile stress in GaN LED films on silicon substrates. It has been reported that the stress will be released to some extent after peeling and transferring to new substrates. Whether the stress of GaN based LED film on silicon substrate can be completely released and then bonded onto the supporting substrate to form a vertical structure chip and whether its photoelectric performance will be improved has not been reported. Although the vertical structure LED of the three technical routes has been commercialized and widely used, and the slight change of the stress after transferring to the new substrate will have a significant effect on the optoelectronic properties of the GaN based LED. However, the initial stress state of the LED thin films with the same structure on the same substrate is still blank. In this paper, GaN based LED thin films with the same epitaxial structure are directly bonded and released respectively to a new supporting substrate. A variety of vertical structure LED chips with different initial stresses are obtained, and their optical and electrical properties are studied. When the LED film is bonded with the substrate by organic flexible bonding layer, the tensile stress of the LED film from the silicon substrate is basically completely released after the silicon substrate is removed. The tensile stress of the LED film will be released both directly and after releasing the stress, and the tensile stress of the chip after releasing the stress will be completely released. However, the tensile stress release of the direct bonding chip is relatively small. 3. In the process of fabricating the GaN based LED chip with vertical structure on the Si substrate, the tensile stress state of the LED film of the direct bonding chip will gradually decrease. The photoluminescence performance of vertical LED chip is not only affected by the initial stress of LED film, but also by the metal bonding between LED film and supporting substrate. Although the pressure stress in the well layer is higher than that in the directly bonded chip, the current Droop effect of the four chips is the same after EQE normalization.
【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】：TN312.8
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，本文编号：2404986
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