中高温插入层对GaN基蓝光LED光电性能的影响

发布时间：2018-05-19 14:04

本文选题：氮化镓 + LED　；参考：《太原理工大学》2016年硕士论文

【摘要】：GaN基LED器件具有发光效率高、能耗低、体积小、显色指数高等优点,在照明、显示等领域的应用越来越广泛。尽管GaN基蓝光LED中位错密度高达108-1010/cm-2,却有40-60%的光电转换效率,这引起科研工作者的兴趣。本文一方面以V形坑屏蔽位错理论为基础,分析了V形坑尺寸对LED光电性能影响,另一方面分析了中高温GaN插入层厚度对LED光电性能的影响。利用金属有机气相化学沉积(MOCVD)技术在蓝宝石图形衬底上生长GaN基蓝光LED,1)通过改变中高温GaN插入层厚度来调控V形坑尺寸,分析了V形坑尺寸对LED光电性能的影响,并对相关的物理机制进行了探讨;2)研究了具有温度梯度插入层的LED器件的光电性能,分析了温度梯度插入层影响LED器件的物理机理。具体研究结果如下:1)利用高分辨X射线衍射仪(HRXRD)、光致发光谱仪(PL)、芯片测试仪、原子力显微镜(AFM)表征了LED器件的结晶质量、光电性能和表面形貌。当中高温GaN插入层厚度从60 nm增加至100 nm时,V形坑尺寸从70-110 nm增加至110-150 nm。V形坑尺寸增大对LED外延片的光学性能的影响为:当激发功率从0.4mW增加至9mW时,峰值波长分别先红移1.8nm和1 nm,然后均蓝移2.8 nm。V形坑尺寸变大对LED器件的电学性能影响为:当注入电流为20 mA时,LED芯片的光功率从21.9 mW增加至24.1 mW,当注入电流从1 mA增加至40 mA时,LED芯片的峰值波长分别蓝移6.5 nm、4.2 nm,半峰宽分别展宽5.9 nm、7.5 nm。通过对V形坑尺寸调控LED光电性能的相关物理机制进行分析,增大V形坑尺寸有利于增加空穴注入面积和注入效率,进而提高LED器件的光功率。2)利用高分辨X射线衍射仪(HRXRD)、光致发光谱仪(PL)、芯片测试仪表征LED器件的结晶质量和光电性能。研究发现:温度梯度GaN插入层使LED外延片的HRXRD(002)面摇摆曲线的半峰宽从290减小至251arsec,(102)面半峰宽从281减小至242 arsec,PL积分强度增加了13.9%,在注入电流为20 mA下,芯片的整体光功率从31.2-32.0 mW增加至33.7-34.5 mW,正向偏压降低约0.1 V。研究结果表明,插入层的温度对LED的光电性能具有重要影响,温度梯度插入层可有效释放LED器件多量子阱中的应力,进而提高LED器件的光电转换效率。
[Abstract]:GaN based LED devices have many advantages, such as high luminescence efficiency, low energy consumption, small volume and high color index, so they are widely used in lighting, display and other fields. Although the dislocation density in GaN based blue light LED is 108-1010 / cm-2, it has a conversion efficiency of 40-60%, which has attracted the interest of researchers. On the one hand, based on the theory of V-shaped pit shielding dislocations, the influence of the size of V-shaped pits on the photoelectric performance of LED is analyzed. On the other hand, the influence of the thickness of GaN intercalation layer at medium and high temperature on the optoelectronic properties of LED is analyzed. GaN based blue light LED1 was grown on sapphire graphic substrate by metal-organic vapor chemical deposition (MOCVD) technique. The size of V-shaped pit was adjusted by changing the thickness of GaN insertion layer at medium and high temperature. The effect of V-shaped pit size on the photoelectric properties of LED was analyzed. The optoelectronic properties of LED devices with temperature gradient insertion layer are investigated. The physical mechanism of the influence of temperature gradient insertion layer on LED devices is analyzed. The results are as follows: (1) the crystal quality, photoelectric properties and surface morphology of LED devices were characterized by high resolution X-ray diffractometer, photoluminescence spectrometer, chip tester and atomic force microscope (AFM). When the intercalation layer thickness of high temperature GaN increases from 60 nm to 100 nm, the effect of increasing the size of V-shaped pits from 70-110 nm to 110-150 nm.V pits on the optical properties of LED epitaxial wafers is as follows: when the excitation power is increased from 0.4mW to 9mW, The peak wavelengths are redshift 1.8nm and 1 nm, respectively, and then the blue shift of 2.8 nm.V hole size increases the electrical performance of LED devices. When the injection current is 20 Ma, the optical power of LED chip is increased from 21.9 MW to 24.1 MW, and when the injection current is from 1 to 1, the optical power of LED chip is increased from 21.9 MW to 24.1 MW. When Ma was increased to 40 Ma, the peak wavelength of LED chip shifted to 6.5 nm and 4.2 nm, respectively, and the half peak width widened by 5.9 nm and 7.5 nm, respectively. Based on the analysis of the physical mechanism of the V-shaped pit size regulating the optoelectronic performance of LED, it is found that increasing the V-shaped pit size is beneficial to increase the hole injection area and injection efficiency. The high resolution X-ray diffractometer, photoluminescence spectrometer and chip tester are used to characterize the crystal quality and optoelectronic properties of LED devices. It is found that the temperature gradient GaN intercalation layer decreases the half peak width of the LED wafer rocking curve from 290 to 251 arsecan 102) surface width from 281 to 242arsecl PL integral intensity increases by 13.9 cm / L at the injection current of 20 Ma. The overall optical power of the chip is increased from 31.2-32.0 MW to 33.7-34.5 MW, and the forward bias is reduced by 0.1 V. The results show that the temperature of the intercalation layer has an important effect on the optoelectronic performance of LED. The temperature gradient intercalation layer can effectively release the stress in multiple quantum wells of LED devices and improve the photoelectric conversion efficiency of LED devices.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN312.8

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