本文選題：Al_xGa_(1-x)N + 金屬有機(jī)物化學(xué)氣相沉積�。� 參考：《東南大學(xué)》2015年博士論文

【摘要】：AlxGa1-xN是直接帶隙寬禁帶半導(dǎo)體材料,化學(xué)性質(zhì)穩(wěn)定,耐高溫,抗輻射,波長(zhǎng)在200～365 nm范圍內(nèi)連續(xù)可調(diào),在空氣凈化、殺菌與消毒、半導(dǎo)體固態(tài)照明等領(lǐng)域具有廣泛的應(yīng)用前景。AlGaN薄膜晶體質(zhì)量對(duì)器件光電性能有很大影響,尤其制備紫外LED所需的高A1組份AlGaN材料的生長(zhǎng)、量子阱結(jié)構(gòu)的設(shè)計(jì)、極化效應(yīng)的影響等一直是制約紫外LED發(fā)展的關(guān)鍵因素。因此,對(duì)AlGaN薄膜生長(zhǎng)和表征的深入研究顯得尤為重要。本論文采用金屬有機(jī)物化學(xué)氣相沉積(MOCVD)的方法制備了高質(zhì)量的不同Al組分的AlGaN薄膜,并且系統(tǒng)地研究了AlGaN材料的物性,進(jìn)而生長(zhǎng)和表征了更具實(shí)用價(jià)值的AlInGaN四元材料的物性,同時(shí)從理論上研究了AlInGaN四元材料對(duì)于提高LED光電性能的影響。通過(guò)對(duì)生長(zhǎng)工藝的優(yōu)化,制備了高質(zhì)量的AlGaN/GaN多量子阱,為制備AlGaN基紫外LED打下了堅(jiān)實(shí)的基礎(chǔ)。另外,對(duì)基于非極性與半極性藍(lán)寶石襯底上的GaN與AlGaN外延生長(zhǎng)進(jìn)行了系統(tǒng)的實(shí)驗(yàn)探究。采用高分辨X射線衍射(HR-XRD)、掃描電子顯微鏡(SEM)、光致發(fā)光譜(PL)、X射線光電子能譜(XPS)、同步輻射X射線光譜等手段,對(duì)外延材料的晶體質(zhì)量、晶格畸變、表面形貌、表面化學(xué)態(tài)和光學(xué)特性進(jìn)行了表征分析。本論文的研究?jī)?nèi)容與取得的成果如下：1. 采用優(yōu)化的MOCVD脈沖生長(zhǎng)工藝,首先在藍(lán)寶石襯底上高溫生長(zhǎng)了AlN緩沖層,進(jìn)而得到了高質(zhì)量的AlxGa1-xN外延薄膜,其中Al組分為0～-87%。并且系統(tǒng)地研究了高溫AlN緩沖層對(duì)減少裂紋密度,提高晶體質(zhì)量的作用。測(cè)試結(jié)果表明當(dāng)高溫AlN緩沖層的厚度為200 nm時(shí),可以極大地改善AlGaN外延層的晶體質(zhì)量。研究還發(fā)現(xiàn)：隨著AlxGa1-xN薄膜中Al組分的增加,晶格發(fā)生了收縮,即晶格常數(shù)c、a以及c/a的比值均有所減��；與之相反的是內(nèi)參數(shù)u的數(shù)值反而隨著Al組分的增加而增大,這種變化趨勢(shì)可以解釋為由于Al的并入增加,Al-N鍵的離子化效應(yīng)增強(qiáng)所導(dǎo)致的。2.采用Raman光譜研究了AlGaN薄膜中應(yīng)力的變化行為。研究結(jié)果表明：AlxGa1-xN薄膜的A1(LO)模式的聲子頻移隨Al組分的變化較為明顯,并且是單模行為；而Al(LO)模式的聲子頻移峰的展寬推測(cè)主要源于AlxGa1-xN薄膜材料中的長(zhǎng)程有序。通過(guò)系統(tǒng)地研究AlxGa1-xN薄膜的光致發(fā)光行為,對(duì)由缺陷態(tài)發(fā)光引起的黃帶機(jī)制做了深入的探討。Al0.26Ga0.74N薄膜樣品的低溫光致發(fā)光譜測(cè)試結(jié)果表明：隨著溫度的降低,由自由載流子復(fù)合引起的317 nm的帶邊發(fā)射峰有“藍(lán)移”的趨勢(shì),并且溫度越低,發(fā)光強(qiáng)度越高,峰值的半高寬也明顯減小。3. 采用同步輻射技術(shù)研究了AlGaN材料的電子結(jié)構(gòu)。通過(guò)分析Ga的K邊延長(zhǎng)的X射線吸收精細(xì)結(jié)構(gòu)光譜(EXAFS)探究了不同殼層原子鍵長(zhǎng)與Al組分的依賴(lài)關(guān)系。研究結(jié)果表明：位于第一殼層的Ga-N鍵長(zhǎng)與Al組分的變化無(wú)關(guān),其值只與離Ga原子最近的N原子相關(guān)；然而第二殼層的Ga-Ga鍵長(zhǎng)與Al組分的關(guān)系較大。計(jì)算結(jié)果發(fā)現(xiàn)Ga-Ga鍵長(zhǎng)要大于Ga-Al鍵長(zhǎng),并且隨著AlxGa1-xN薄膜樣品中Al組分的增加,Ga-Ga鍵長(zhǎng)有減小的趨勢(shì),分析這可能與Al原子的原子半徑較小有關(guān)。本論文還進(jìn)一步地研究了AlxGa1-xN薄膜的表面化學(xué)態(tài)。通過(guò)測(cè)量Ga 3d、Al 2p, N Is的XPS能譜,以及對(duì)XPS能譜進(jìn)行擬合,分析研究了AlxGa1-xN薄膜表面的氧化行為。結(jié)果顯示：AlxGa1-xN薄膜樣品表面同時(shí)存在著氮化物與氧化物,并且隨著Al組分的增加,Al的氧化要強(qiáng)于Ga的氧化。研究還發(fā)現(xiàn),Ga的俄歇躍遷與O-Ga鍵或者Ga的其他化合物相關(guān)。4. 探究了AlInGaN四元材料的生長(zhǎng)工藝,系統(tǒng)地研究了生長(zhǎng)溫度對(duì)相分離現(xiàn)象的影響和富In區(qū)域形成的物理機(jī)制,優(yōu)化得到較為理想的生長(zhǎng)溫度為890℃。光致發(fā)光譜測(cè)試結(jié)果表明隨著生長(zhǎng)壓力的減小,缺陷雜質(zhì)發(fā)光得到抑制,說(shuō)明較低的生長(zhǎng)壓力會(huì)改善AlInGaN薄膜的晶體質(zhì)量,發(fā)現(xiàn)其中的“Ⅴ”型缺陷的密度和尺寸都隨著壓力的降低而減��；高Al/In摩爾比會(huì)抑制AlInGaN薄膜中的相分離,可能是因?yàn)楦籌n團(tuán)簇的減少導(dǎo)致了這一結(jié)果。通過(guò)Raman光譜測(cè)量驗(yàn)證了AlInGaN四元薄膜中確實(shí)存在In的團(tuán)簇,同時(shí)該結(jié)論也說(shuō)明了“Ⅴ”型缺陷的來(lái)源與In的并入有很大關(guān)系。AlInGaN四元薄膜的變溫光致發(fā)光譜揭示了AlInGaN發(fā)光峰峰值能量隨溫度的變化呈“S”形變化的關(guān)系,并對(duì)這一現(xiàn)象作了合理的解釋。5.深入研究了AlGaN/GaN多量子阱的生長(zhǎng)工藝條件,特別是異質(zhì)結(jié)界面的H2吹掃時(shí)間對(duì)量子阱界面質(zhì)量與光學(xué)性能的影響。實(shí)驗(yàn)發(fā)現(xiàn),當(dāng)生長(zhǎng)AlGaN勢(shì)壘層后的H2吹掃時(shí)間為4分鐘,生長(zhǎng)GaN阱層后H2的吹掃時(shí)間為2分鐘時(shí),可以獲得界面平滑、組分變化陡峻的量子阱界面。通過(guò)對(duì)量子阱界面質(zhì)量的分析,進(jìn)一步探討了量子阱中的缺陷形成機(jī)制。在此基礎(chǔ)上,并通過(guò)優(yōu)化生長(zhǎng)工藝條件,最終制備得到了高質(zhì)量、界面清晰的AlGaN/GaN多量子阱樣品。光致發(fā)光譜測(cè)試結(jié)果表明,由于存在內(nèi)建電場(chǎng),因量子限制斯塔克效應(yīng)引起的能帶彎曲,導(dǎo)致了AlGaN/GaN多量子阱發(fā)光峰的“紅移”；而當(dāng)量子阱寬降低時(shí),量子限制效應(yīng)占主導(dǎo)地位,導(dǎo)致發(fā)光峰波長(zhǎng)的“藍(lán)移”。6.對(duì)半極性R面與非極性A面、M面藍(lán)寶石襯底上GaN與AlGaN的外延生長(zhǎng)工藝進(jìn)行了優(yōu)化。發(fā)現(xiàn)生長(zhǎng)成核層時(shí)采用高的Ⅴ/Ⅲ比有利于改善GaN外延薄膜的晶體質(zhì)量,但所獲得的晶體為沿著c[0001]方向生長(zhǎng)的極性材料。本研究也在非極性M面藍(lán)寶石襯底上進(jìn)行了GaN材料的生長(zhǎng),獲得了晶體質(zhì)量較好的具有[1122]晶向的半極性樣品。本研究還在A面和M面藍(lán)寶石襯底上生長(zhǎng)了AlGaN材料,并且進(jìn)行了Si摻雜。發(fā)現(xiàn)在A面襯底上生長(zhǎng)的AlGaN經(jīng)過(guò)Si摻雜后表面形貌和晶體質(zhì)量都得到了改善,C的并入量有所減少,藍(lán)帶發(fā)光強(qiáng)度減弱。而在M面藍(lán)寶石襯底上生長(zhǎng)的AlGaN經(jīng)過(guò)Si摻雜以后,表面形貌和晶體質(zhì)量卻有所下降,C的并入量增加,藍(lán)帶發(fā)光強(qiáng)度減弱。本研究所開(kāi)展的半極性、非極性GaN和AlGaN材料的生長(zhǎng)實(shí)驗(yàn),為制備高亮度非極性AlGaN基紫外LED打下了堅(jiān)實(shí)的基礎(chǔ)。7. 采用APSYS光學(xué)器件模擬軟件分析計(jì)算了p-AlInGaN四元材料以及p-AlInGaN/GaN超晶格結(jié)構(gòu)作為GaN基LED電子阻擋層對(duì)LED芯片光電性能的影響。通過(guò)對(duì)量子阱中的極化電場(chǎng)以及極化場(chǎng)下能帶結(jié)構(gòu)、載流子濃度分布、自發(fā)輻射復(fù)合速率的研究,發(fā)現(xiàn)采用與GaN晶格匹配的p-In0.018Al0.089Ga0.893N/GaN超晶格作為電子阻擋層,不僅可以減小由于極化電場(chǎng)引起的能帶彎曲效應(yīng),而且通過(guò)p-GaN層注入到有源區(qū)的空穴注入效率得到了很大的提高,同時(shí)漏電流也獲得明顯減小。并且在大電流注入條件下,研究結(jié)果表明采用p-In0.018Al0.089Ga0.893N/GaN超晶格電子阻擋層結(jié)構(gòu)的GaN基LED的“效率下降”現(xiàn)象得到了明顯的改善。
[Abstract]:AlxGa1-xN is a direct band gap wide band gap semiconductor material with stable chemical properties, high temperature resistance, radiation resistance and continuous adjustable wavelength in the range of 200~365 nm. It has a wide application prospect in the fields of air purification, sterilization and disinfection, semiconductor solid-state lighting and so on. The crystal quantity of.AlGaN films has a great influence on the photoelectric properties of the devices, especially in the preparation of UV. The growth of high A1 component AlGaN material required by LED, the design of quantum well structure and the influence of polarization effect have been the key factors that restrict the development of UV LED. Therefore, it is very important to study the growth and characterization of AlGaN thin films. This paper uses the method of chemical vapor deposition of metal organic compounds (MOCVD) to prepare the high quality. The physical properties of AlGaN materials are systematically studied with the AlGaN film of the Al component, and the physical properties of the more practical AlInGaN four element materials are grown and characterized. At the same time, the effect of AlInGaN four yuan material on improving the photoelectric properties of LED is theoretically studied. The high quality AlGaN/GaN multi quantum is prepared by optimizing the growth process. Well, a solid foundation was laid for the preparation of AlGaN based UV LED. In addition, a systematic experiment was carried out on the epitaxial growth of GaN and AlGaN based on the non polar and semi polar sapphire substrates. High resolution X ray diffraction (HR-XRD), scanning electron microscopy (SEM), photoluminescence (PL), X ray photoelectron spectroscopy (XPS), and synchrotron radiation X ray were used. The crystal quality, lattice distortion, surface morphology, surface chemical and optical properties of the epitaxial materials are characterized by spectroscopic methods. The contents and achievements of this paper are as follows: 1. the AlN buffer layer was first grown on the sapphire substrate by the optimized MOCVD pulse growth process, and the high quality was obtained. The AlxGa1-xN epitaxial film, in which the Al group is divided into 0 ~ -87%., and the effect of the high temperature AlN buffer layer on reducing the crack density and improving the crystal quality is systematically studied. The test results show that when the thickness of the high temperature AlN buffer layer is 200 nm, the crystal quality of the AlGaN epitaxial layer can be greatly improved. The study also shows that with the Al in the AlxGa1-xN thin film, the crystal quality can be greatly improved. With the increase of the component, the lattice of the lattice is contracted, that is, the ratio of the lattice constant C, a and c/a decreases. In contrast, the internal parameter u increases with the increase of the Al component. This trend can be explained by the Raman spectrum studied by Raman spectrum due to the increase of Al's incorporation and the enhancement of the ionization effect of the Al-N bond. The change of stress in the GaN film shows that the phonon shift of the A1 (LO) mode of the AlxGa1-xN film is more obvious with the change of the Al component, and it is a single mode behavior, while the broadening of the phonon frequency shift peak in the Al (LO) mode is mainly derived from the long range order in the AlxGa1-xN film material. The light of the AlxGa1-xN thin film is systematically studied. The luminescence behavior and the mechanism of the yellow band caused by the defect state luminescence have been deeply discussed. The results of low temperature photoluminescence spectrum test of.Al0.26Ga0.74N film samples show that with the decrease of temperature, the 317 nm edge emission peak caused by free carrier recombination has a "blue shift" trend, and the lower the temperature, the higher the luminescence intensity, the peak value. The electronic structure of AlGaN materials was studied by.3. by synchrotron radiation technology. The dependence of the bond length of different shell atoms and the Al component was investigated by analyzing the X ray absorption fine structure spectrum (EXAFS) of the K edge extension of Ga. The results showed that the Ga-N bond length in the first shell was independent of the Al component. Its value is only related to the N atom nearest to the Ga atom; however, the length of the Ga-Ga bond of the second shell is closely related to the Al component. The calculation results show that the length of the Ga-Ga bond is larger than the Ga-Al bond length, and the Ga-Ga bond length decreases with the increase of the Al component in the AlxGa1-xN film samples. This analysis may be related to the smaller atomic radius of the Al atom. The surface chemical state of the AlxGa1-xN film is further studied. By measuring the XPS energy spectrum of Ga 3D, Al 2p, N Is and the fitting of the XPS spectrum, the oxidation behavior of the AlxGa1-xN film surface is analyzed and studied. The results show that there is a nitride and oxide on the surface of the AlxGa1-xN film sample and the increase of the Al components. The oxidation of L is stronger than the oxidation of Ga. It is also found that the Ga's auger transition is related to the O-Ga bond or other compounds associated with Ga to explore the growth process of the AlInGaN four element material, and systematically study the effect of the growth temperature on the phase separation and the physical mechanism of the formation of the rich In region. The optimum growth temperature is 890. The results of the hair spectrum test show that with the decrease of the growth pressure, the luminescence of the defective impurities is suppressed. It shows that the lower growth pressure will improve the crystal quality of the AlInGaN film. It is found that the density and size of the "V" type defects decrease with the decrease of pressure, and the high Al/In molar ratio will inhibit the phase separation in the AlInGaN film. This result is caused by the reduction of the rich In cluster. The cluster of In in the AlInGaN four element film is verified by the Raman spectrum measurement. The conclusion also shows that the origin of the "V" type defect and the incorporation of In have a great relationship with the.AlInGaN four element thin film, which reveals the peak energy of the AlInGaN luminescence peak. The change of temperature shows a "S" shape change, and a reasonable explanation of this phenomenon is made by.5.. The growth process conditions of AlGaN/GaN multiple quantum well are deeply studied, especially the influence of H2 blowing time on the quality and optical properties of the quantum well interface at the heterojunction interface. The experiment shows that the time of H2 blowing after the growth of the AlGaN barrier layer is 4. When the blower time of the GaN well layer is 2 minutes after the growth of the well, the interface is smooth and the composition of the quantum well can be precipitous. By analyzing the quality of the quantum well interface, the formation mechanism of the defect in the quantum well is further discussed. On this basis, the high quality, the interface clear is obtained by optimizing the growth process conditions. The results of photoluminescence spectrum test show that due to the existence of the built-in electric field, the band bending caused by the quantum confinement effect leads to the "red shift" of the luminescence peak of the AlGaN/GaN multi quantum well, while the quantum confinement effect should dominate when the width of the quantum well is reduced, leading to the "blue shift" of the wavelength of the luminescence peak. ".6. has optimized the epitaxial growth process of GaN and AlGaN on the semi polar R surface and non polar A surface and M surface sapphire substrate. It is found that the high V / III ratio is beneficial to improve the crystal quality of the GaN epitaxial film when the nucleation layer is growing, but the obtained crystal is a polar material along the c[0001] direction. This study is also in the non polar M surface blue. The GaN material was grown on the gem substrate, and the crystal quality with [1122] crystal direction was obtained. The AlGaN material was grown on the A surface and the M surface sapphire substrate, and the Si doping was carried out. It was found that the surface morphology and crystal quality of AlGaN grown on the A substrate were improved after Si doping, C. The absorption of the blue band decreases and the luminescence intensity of the blue band is weakened. The surface morphology and crystal quality of the AlGaN grown on the M sapphire substrate has declined after the Si doping, and the incorporation of C is increased and the luminescence intensity of the blue band is weakened. The growth experiments of the semi polar, non polar GaN and AlGaN materials in this study are to prepare the high brightness non polar. The sexual AlGaN based UV LED lays a solid foundation.7. using APSYS optical device simulation software to analyze and calculate the effect of p-AlInGaN four yuan material and p-AlInGaN/GaN superlattice as the GaN based LED electronic barrier layer on the optoelectronic properties of LED chip. By the polarization field in the quantum well and the band structure under the polarization field, the carrier concentration Distribution, the study of the spontaneous radiation recombination rate, it is found that using the p-In0.018Al0.089Ga0.893N/GaN superlattice matched with the GaN lattice as the electronic barrier layer, it can not only reduce the band bending effect caused by the polarization electric field, but also improve the cavity injection efficiency by injecting the p-GaN layer into the active region, and the leakage current also is also improved. The results are obviously reduced and the results show that the "efficiency decline" of the GaN based LED with the structure of the p-In0.018Al0.089Ga0.893N/GaN superlattice is obviously improved under the condition of high current injection.

【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TN312.8

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相關(guān)期刊論文 前10條

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本文編號(hào)：1837141