HB-LED器件结构研究

【作者】 刘鲁；

【导师】 范广涵； 廖常俊；

【作者基本信息】 华南师范大学 ， 微电子学与固体电子学， 2003， 硕士

【摘要】 如何提高高亮度发光二极管(HB-LED)的亮度是一项极具理论和经济效益的课题。实践证明，通过改变器件结构可以大大提高HB-LED的亮度。 本论文结合完成的超高亮度发光二极管半工业化实验项目，提出了改进的HB-LED器件结构，提高了LED亮度。采用p-N渐变异质结替代现行的p-N突变异质结，不仅有效提高了发光亮度，而且改善了器件质量。 本文从理论上分析此结构改进的合理性和有效性，得到一系列地结论。并且用双层突变拟合渐变方式进行芯片生长，实验结果符合理论分析。 本文还针对高亮度发光二极管的器件结构中重要的双异质结结构(DH)和多量子阱(MQW)结构进行了系统的，深入的分析和研究。分析了每一种结构在载流子输运、载流子限制和复合等方面产生的作用，从而阐明了这两器件结构是如何提高HB-LED的发光亮度。 本文的主要工作如下： 1．在理论上提出在HB-LED器件的DH结构中使用p-N结的渐变异质结替代现行的p-N突变异质结。分析采用异质结渐变方式将增加HB-LED的电流注入比，减小内建电势，改善晶体质量，并且不影响p-N结对空穴的限制。此举将会有效提高发光亮度。 2．通过模拟不同渐变长度下的能带形状，得出结论：不同渐变长度下，最佳渐变方式并不相同。渐变长度较短时，高斯渐变和抛物线渐变是最佳渐变方式，能带形状更适合载流子输运。渐变长度较长时，线性渐变是最佳渐变方式，能带形状更适合载流子输运。 3．在三种不同掺杂情况下，通过数值模拟得出消除能带尖峰所需的最小渐变长度。并且得出结论：N型掺杂浓度越高，消除尖峰所需的渐变长度越短。 4．由于渐变异质结在实现上存在一定的困难，因此我们提出了用双层突变异质结拟合渐变异质结。并且通过拟合能带边，得出最佳的两层组分分配。通过计算，得出第二层的最佳突变位置。并且从实验结果看，双层突变异质结有效提高发光亮度，改善了器件参数，晶体质量变好。 5．通过推导，得出一个计算化合物半导体异质结内建电势的公式。内建电势是一个重要的参数，通过它可以得到很多异质结的相关参数。得出的公式与相比传统公式更简单、实用。并且准确度较高。 6．全面分析双异质结结构(DH)在HB-LED中的重要作用。DH结构不仅提高了载流子注入比并且加强了载流子限制作用，提高了辐射复合的效率，使得HB-LED的亮度大幅度提高。并且引入模拟异质结的数学模型。总结异质结生长方面的问题。 7．全面分析多量子阱结构(MQW)在HB-LED中的重要作用。采用MQW结构可以减小相同发射波长下材料中的铝组分，从而改善了晶体大的质量。MQW结构比DH结构更加有效的限制载流子，增加辐射复合效率。从而提高了发光亮度。总结了MQW生长。引入了模拟MQW的数学模型。更多还原

【Abstract】 How to enhance the brightness of High Brightness Light Emitting Diode is a valuable problem in theory and in economy. Improving the structure of the chip can greatly enhance the brightness of LED.In this thesis, the effects of applying p-N graded heterojunction instead of p-N abrupt heterojunction have been analyzed theoretically and manufactured experimentally, and great progress has been obtained.In this thesis, each structure in the LED chip has analyzed deeply and systematically. The effect of each structure on the transfer of the carrier, the confinement of the carrier, the recombination of the carrier has been analyzed.The main work is showed as follow:1. Appling p-N graded heterojunction instead of abrupt one is studied deeply in theory, and the conclusion is that it will enhance the current injection ratio, decrease the built- in voltage, improve the quality of the crystal and it will not affect the confinement to the hole. It enhances the brightness effectively.2. The band profile is simulated by the mathematic way. We get the conclusion. When the grading length is comparatively short, the best grading way are Gath and parabolic way. When the grading length is comparatively long, the lineral grading way is the best one. Under the best grading way, the shape of the band profile is more propitious to the transfer of the carrier.3. Under the three different doping densities, we get the least grading length to make the spike vanish. We get the conclusion: The higher the doping density is ,the shorter grading length is wanted to make the spike vanish.4. As there is some difficulty to manufacture the graded heterojunction, we put forward that it can use double layer abrupt heteojunction to take the place of the graded heterojunction. We get the best distributions of the two layer and the best abrupt position. From the result of the practice, this structure enhances the brightness of LED effectively, improves the quality of the crystal and improves the performance of the device.5. A formula is deduced to calculate the built-in voltage of the compound semiconductor. We can get some important parameters from the built-in voltage. The formula is more simply and useful than the orthodox one, and the accuracy is high.6. The effect of the DH on the HB-LED is analyzed. Applying DH can enhance the injection ratio, strengthen the confinement to the carrier and enhanced the efficiency of the recombination. This make the brightness greatly enhance. The mathematic model of DH is educed. The growth of DH is summarized.7. The effect of the MQW on the HB-LED is analyzed. Al content will decrease if using MQW even the same emitting wavelength. And it will improve the quality of the crystal. MQW have the same effect on HB-LED as DH, but better than that. The mathematic model is educed. The growth of MQW is summarized.更多还原