本文關(guān)鍵詞： AlGaN MOCVD 分布式布拉格反射鏡 紫外LED　出處：《吉林大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：隨著GaN基發(fā)光二極管(LED)研發(fā)的不斷深入,其技術(shù)創(chuàng)新與應(yīng)用領(lǐng)域也在不斷拓展,以AlGaN作為有源區(qū)的紫外LED逐漸成為研究重點(diǎn)。AlGaN基紫外LED在固化、醫(yī)療、短距離通信等領(lǐng)域有重要應(yīng)用價(jià)值。且相較于傳統(tǒng)的紫外光源,具有高效節(jié)能、無(wú)汞環(huán)保、可靠耐用、體積小等優(yōu)點(diǎn)。另外,由于分布式布拉格反射鏡(DBR)可以反射特定波長(zhǎng)的光,已被廣泛應(yīng)用到發(fā)光器件中以提高光提取效率。在本文中,我們分別在藍(lán)寶石襯底和SiC襯底上開(kāi)展了AlGaN基紫外DBR的制備工作,并基于SiC襯底初步研制了帶有DBR的紫外LED,具體工作如下:我們從理論上計(jì)算分析了生長(zhǎng)在藍(lán)寶石襯底/GaN模板層上的AlxGa1-xN薄膜開(kāi)裂臨界厚度與Al組分x之間關(guān)系,并結(jié)合實(shí)驗(yàn)中外延得到的不同厚度AlGaN薄膜開(kāi)裂情況與Al組分值之間的關(guān)系驗(yàn)證了理論計(jì)算結(jié)果的可靠性。實(shí)驗(yàn)上,我們利用金屬有機(jī)物化學(xué)氣相沉積(MOCVD)方法在藍(lán)寶石襯底上制備AlGaN/GaN DBR,通過(guò)引入低溫AlN插入層調(diào)控薄膜內(nèi)應(yīng)力,獲得了無(wú)裂紋的AlGaN/GaN DBR。我們又研究了Al N插入層對(duì)DBR特性的影響,發(fā)現(xiàn)低溫AlN插入層的引入在防止裂紋產(chǎn)生的同時(shí)會(huì)引起外延層表面平整度退化,這可能是由不平整的低溫AlN插入層表面造成的。隨著DBR對(duì)數(shù)的增加,其表面平整度得到逐步改善。經(jīng)過(guò)系列實(shí)驗(yàn),我們?cè)谒{(lán)寶石襯底上制備得到了中心波長(zhǎng)在390 nm,峰值反射率為94%,阻帶寬度16 nm的25對(duì)無(wú)裂紋Al0.32Ga0.68N/GaN DBR,其表面粗糙度為0.46nm。為下一步研制帶有DBR的近紫外LED奠定了基礎(chǔ)。相比于藍(lán)寶石襯底,SiC襯底與AlGaN晶格失配小,可有效改善AlGaN外延層晶體質(zhì)量。同時(shí),SiC襯底良好的導(dǎo)電性能使其可以被用來(lái)外延制備垂直導(dǎo)電結(jié)構(gòu)LED,與水平結(jié)構(gòu)相比垂直結(jié)構(gòu)LED可以有效解決電流擁堵現(xiàn)象,提高有源區(qū)利用率。我們?cè)趎型6H-SiC襯底上制備了Si摻雜AlGaN基DBR,通過(guò)引入低溫AlN模板層,獲得了表面均方根粗糙度為0.4 nm且導(dǎo)電性能良好的15對(duì)無(wú)裂紋n型Al0.19Ga0.81N/Al0.37Ga0.63N DBR,其在369 nm處峰值反射率為68%,阻帶寬度為10 nm。在獲得導(dǎo)電DBR的基礎(chǔ)上,我們進(jìn)一步在n型6H-SiC襯底上構(gòu)建了有、無(wú)DBR的垂直結(jié)構(gòu)紫外LED。對(duì)比兩者電致發(fā)光光譜,發(fā)現(xiàn)DBR結(jié)構(gòu)的引入可以明顯增強(qiáng)LED紫外發(fā)光強(qiáng)度。
[Abstract]:With the development of GaN based LED, its technology innovation and application fields are also expanding. Ultraviolet LED with AlGaN as its active region is becoming the focus of research. AlGaN-based UV LED is solidified and treated. Short distance communication and other fields have important application value. Compared with traditional ultraviolet light sources, they have the advantages of high efficiency, energy saving, no mercury, environmental protection, reliability, durability, small size, etc. Distributed Bragg reflector (DBR) can reflect light of specific wavelength, so it has been widely used in light-emitting devices to improve the efficiency of optical extraction. We have prepared AlGaN based UV DBR on sapphire and SiC substrates, respectively. Based on SiC substrate, UV LED with DBR has been developed. The main work is as follows: we calculated and analyzed the relationship between critical cracking thickness of AlxGa1-xN film grown on sapphire substrate / gan template layer and Al component x. The reliability of the calculated results is verified by the relationship between the cracking of AlGaN thin films with different thickness and the Al component in the experiment. AlGaN/GaN DBRs were prepared on sapphire substrates by metal-organic chemical vapor deposition (MOCVD) method. The crack free AlGaN/GaN DBRs were obtained by introducing a low temperature AlN intercalation layer to regulate the internal stress of the films. We also studied the effect of the AlN intercalation layer on the DBR properties. It is found that the introduction of the low temperature AlN intercalation layer can not only prevent the formation of cracks, but also cause the degradation of the surface smoothness of the epitaxial layer, which may be caused by the uneven low temperature AlN intercalation layer surface. With the increase of the DBR logarithm, Its surface smoothness has been gradually improved. After a series of experiments, We have prepared on sapphire substrates 25 pairs of crack-free Al0.32Ga0.68N/GaN DBRs with a central wavelength of 390nm, a peak reflectivity of 94nm and a stopband width of 16nm, the surface roughness of which is 0.46nm. this will lay a foundation for the next development of near-ultraviolet LED with DBR. The lattice mismatch between sic substrate and AlGaN substrate is smaller than that on sapphire substrate. The crystal quality of AlGaN epitaxial layer can be improved effectively. At the same time, sic substrate can be used to epitaxially fabricate vertical conductive structure. Compared with horizontal structure, vertical structure LED can effectively solve the problem of current congestion. We prepared Si-doped AlGaN based DBRs on n-type 6H-SiC substrates by introducing low temperature AlN template layer. Fifteen pairs of crack free n-mode Al0.19Ga0.81N/Al0.37Ga0.63N DBRs with a surface RMS roughness of 0.4 nm and good conductivity were obtained. The peak reflectivity at 369 nm was 68 and the stopband width was 10 nm. On the basis of obtaining conductive DBR, We have further constructed the vertical structure LED with and without DBR on n-type 6H-SiC substrates. Compared with the electroluminescent spectra, it is found that the introduction of DBR structure can obviously enhance the UV luminescence intensity of LED.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN312.8

【參考文獻(xiàn)】

相關(guān)期刊論文 前5條

1 李晉閩;劉U，

本文編號(hào)：1499835