【作者】 郑畅达；

【导师】 江风益；

【作者基本信息】 南昌大学 ， 材料物理与化学， 2014， 博士

【摘要】 以GaN基LED芯片为基础的固态照明器件具有发光效率高，寿命长，响应速度快，发光强度随电流和脉冲宽度近线性变化，能在剧烈振动和恶劣环境下工作，不含环境有害物质等优点，成为新一代通用照明灯具的首选。随着研究的深入和产业的发展，GaN基发光二极管的材料生长和器件制造技术已经取得了长足进步，器件效率和可靠性也有显著提升；特别是硅衬底GaN LED外延技术和芯片制造技术的成功实施，芯片成本进一步下降，加速了LED灯全面取代白炽灯和荧光灯进入通用照明领域的进程。在此背景下，本文开展了对硅衬底GaN基材料和器件生长的研究。论文首先对Al合金掩膜微图形化Si(111)衬底上GaN材料的侧向外延生长进行了研究；然后，研究了同温cap层和cap层厚度对绿光InGaN/GaN MQWs LEDs量子阱材料质量和芯片发光性能的影响，以及湿法表面粗化对蓝光LED芯片取光效率的提升作用；最后，对硅衬底GaN垂直结构大功率发光二极管的可靠性进行了研究分析。通过上述研究，本论文取得了以下主要结果：1.提出了用于硅衬底GaN材料选区外延生长的Al-Si合金掩膜技术。通过在Si(111)衬底表面蒸镀150金属Al，经光刻工艺制作Al金属图形，然后高温1200℃下进行合金扩散，获得了Al-Si合金掩膜的图形化硅衬底。实验表明，在Al-Si合金掩膜区不会生长GaN，因此，Al-Si合金技术是Si衬底上选区外延生长GaN材料的一种有效掩膜方法。2.通过优化Al-Si合金条形掩膜参数和GaN外延生长条件，成功地在Al-Si合金掩膜微图形化Si(111)衬底上的周期为1mm1mm方块区域内生长出无裂纹GaN连续外延膜，并通过在方块之间Al-Si掩膜区的硅衬底内产生裂纹，实现了应力释放，从而有效地解决了硅衬底GaN外延膜发生龟裂的难题。3.通过引入阱后同温GaN cap层，成功地实现了对InGaN/GaN多量子阱绿光LED低温生长的阱层InGaN材料的保护作用。研究表明，cap层厚度在一定范围内增加，InGaN阱层的In组分升高且分布更均匀，InGaN材料质量和量子阱界面特性变好。具有25cap层的绿光器件的外量子效率(EQE)及EQE最高值对应的电流密度分别是15cap层器件的1.39倍和10倍，文中对此给出了相应解释。4.经过工艺优化，研制的厚度为25cap层结构的硅衬底垂直结构绿光LED芯片，经封装在350mA直流驱动下(电流密度35A/cm2)，主波长为519nm，内量子效率40.3%，工作电压2.99V，光功率达235mW，这是目前报道的硅衬底绿光发光二极管最好水平。5.通过引入500Torr高压条件下生长的p-GaN层，在具有大V型坑结构的InGaN/GaN蓝光LED外延结构中，成功地实现了对量子阱区V型坑的填平作用，芯片反向漏电下降，器件发光效率增大；通过工艺优化，研制的具有此结构外延片制造的垂直结构大功率蓝光LED芯片在350mA直流驱动下(电流密度35A/cm2)，主波长为450nm，内量子效率达79.5%，硅胶封装器件的工作电压为3.05V，光功率达595mW，与蓝宝石衬底蓝光LED市场产品的先进水平持平，从而有力地表明硅衬底LED是一条行之有效的半导体照明新技术路线。更多还原

【Abstract】 Solid State lighting lamps with GaN based LED chips are considered as thepreferred candidates for the next generation lighting, due to their high efficiency,long lifetime, fast modulation speed, good robustness to shocks and atmosphericagents, near linear behavior under continuous current and pulsed width, and free ofmercury. As the research and industrialization carry forward, the material growthand device manufacture technology has made great advancements over the years.Chip efficiency and reliability has also been greatly improved. Especially, thesuccessful growth of GaN and fabrication of high efficiency LED chips on siliconsubstrates has further cut the device cost, which speeds up the replacement ofincandescent lamps and fluorescent lamps as the generation lamps.Under this background, this dissertation focuses on the growth of GaN materialand LED device on silicon substrates. Firstly, lateral epitaxial overgrowth of GaNsubstrate was investigated on patterned Si (111) substrates with annealed Al-Si alloyfilm as mask and the epitaxial growth of GaN LED structure was studied on Si (111)substrates with different resistivity. Secondly, same temperature cap layer wasinduced after quantum well in green LED. The effect of cap layer thickness on thequality of QW InGaN materials and photoluminescence spectra of InGaN/GaNLEDs was researched. The efficiency improvement of blue GaN LED was alsostudied by n-GaN surface roughening with40%NaOH solution at80℃for10minutes. Lastly, the reliability of high-power vertical GaN LEDs on silicon wasstudied.The following innovative and meaningful research results were conluded：1、 Al-Si alloy mask was formed by evaporating150Al metal film on silicon(111)substrate, Al film patterning and annealing at1200℃. The results show thanAlN and GaN can’t be nucleated on Al-Si alloy mask. So, Al-Si alloytechnology is an effective mask for GaN selective-area growth on siliconsubstrates. 2、 Epitaxial lateral growth GaN was studied on patterned Si (111) substrate with5μm period square Al-Si alloy layer as mask. When the square area is siliconsurface, only pyramid-shaped selective-area growth GaN crystal can be formedwith six GaN {1-100} planes exposed. When square area is covered by Al-Sialloy mask, GaN reticular films covered the silicon film and mask square can’tbe fully covered with forming a reversed pyramid voids on it3、 Epitaxial lateral growth GaN was studied on patterned Si (111) substrate with4μm period stripy Al-Si alloy layer as mask. When the mask stripes are parallelto GaN [11-20] directon, only Independent triangle GaN stripes can be grownon the Si substrate. When the mask stripe are Parallel to GaN[1-100] direction,the lateral epitaxy overgrowth was improved and crack-free GaN crystalcontinuous films were successfully grown on the Al-Si alloy masked Si (111)substrate by increasing growth temperature and decreasing growth pressure.4、 Same temperature (ST) GaN cap layer after QW was induced in InGaN/GaNMQWs green LED. Relative thicker cap layer is benefit to promote Incomponent, homogeneity of InGaN well, and the interaface abruptnessof theMQWs. The n-GaN roughened vertical green LED with25cap layer haslarger quantum conversion efficiency. Under35A/cm2direct current（DC）driven, the1140um1140μm silica pakeaged LED has28.1%EQE,235mWoutput power,519nm domain wavelength and2.99V operating voltage.5、 P-GaN layer under500Torr pressure was induced in the LED epitaxial layerhaving big V-pits in InGaN/GaN MQWs. The results show that thehigh-pressure P-GaN layer could effectively landfill the V-pits, reduce reverselakage current and improve lighting efficiency. Under35A/cm2DC driven, the11400um1140μm vertical blue LED chip with high-pressure layer has79.5%IQE. The silica pakeaged LED has595mW output power,450nm domainwavelength and3.05V operating voltage.更多还原