插入δAl/AlN缓冲层在Si(111)上生长GaN

采用MOCVD(metal organic chemical vapor deposition)生长方法,对比在AlN层上加入δAl/AlN缓冲层和不加入δAl/AlN缓冲层两种生长结构,在Si(111)衬底上生长GaN.实验结果表明,在加入δAl/AlN缓冲层后,GaN外延层的裂纹密度得到了有效的降低,晶体质量也得到了明显的提高.通过MOCVD生长方法,利用光学显微镜、XRD和Raman等分析测试手段,研究了δAl/AlN缓冲层对GaN外延层的影响,获得了裂纹密度小、晶体质量高的GaN材料.     

插入δAl/AlN缓冲层在Si(111)上生长GaN

采用MOCVD(metal organic chemical vapor deposition)生长方法,对比在AlN层上加入δAl/AlN缓冲层和不加入δAl/AlN缓冲层两种生长结构,在Si(111)衬底上生长GaN.实验结果表明,在加入δAl/AlN缓冲层后,GaN外延层的裂纹密度得到了有效的降低,晶体质量也得到了明显的提高.通过MOCVD生长方法,利用光学显微镜、XRD和Raman等分析测试手段,研究了δAl/AlN缓冲层对GaN外延层的影响,获得了裂纹密度小、晶体质量高的GaN材料.     

预辅Al及AlN缓冲层厚度对GaN/Si(111)材料特性的影响

主要研究了采用高温AlN缓冲层外延生长GaN/Si(111)材料的工艺技术。利用高分辨X射线双晶衍射(HRXRD)分析研究了GaN/Si(111)样品外延层的应变状态和晶体质量,通过原子力显微镜(AFM)分析研究了不同厚度的高温AlN缓冲层对GaN外延层的表面形貌的影响。实验结果表明,AlN缓冲层生长前预通三甲基铝(TMAl)的时间、AlN缓冲层的厚度对GaN外延层的应变状态、外延层的晶体质量以及表面形貌都有显著影响。得到最优的预辅Al时间为10s,AlN缓冲层的厚度为40nm。在此条件下外延生长的GaN样品(厚度约为1μm)表面形貌较好,X射线衍射(XRD)双晶摇摆曲线半峰全宽(FWHM)(0002)面和(10-12)面分别为452″和722″。     

AlN缓冲层厚度对脉冲激光沉积技术生长的GaN薄膜性能的影响

在蓝宝石(Al2O3)衬底上应用脉冲激光沉积技术(PLD)生长不同厚度的AlN缓冲层后进行GaN薄膜外延生长。采用高分辨X射线衍射仪(HRXRD)和扫描电子显微镜(SEM)对外延生长所得GaN薄膜的晶体质量和表面形貌进行了表征。测试结果表明:相比直接在Al2O3衬底上生长的GaN薄膜,通过生长AlN缓冲层的GaN薄膜虽然晶体质量较差,但表面较平整;而且随着AlN缓冲层厚度的增加,GaN薄膜的晶体质量和表面平整度均逐渐提高。可见,AlN缓冲层厚度对在Al2O3衬底上外延生长GaN薄膜的晶体质量和表面形貌有着重要的影响。     

AlN缓冲层厚度对脉冲激光沉积技术生长的GaN薄膜性能的影响

在蓝宝石(Al2O3)衬底上应用脉冲激光沉积技术(PLD)生长不同厚度的AlN缓冲层后进行GaN薄膜外延生长。采用高分辨X射线衍射仪(HRXRD)和扫描电子显微镜(SEM)对外延生长所得GaN薄膜的晶体质量和表面形貌进行了表征。测试结果表明: 相比直接在Al2O3衬底上生长的GaN薄膜, 通过生长AlN缓冲层的GaN薄膜虽然晶体质量较差, 但表面较平整; 而且随着AlN缓冲层厚度的增加, GaN薄膜的晶体质量和表面平整度均逐渐提高。可见, AlN缓冲层厚度对在Al2O3衬底上外延生长GaN薄膜的晶体质量和表面形貌有着重要的影响。     

引入GaN过渡层对Si（111）衬底上生长GaN外延的影响

本文研究了在Si(111)衬底上生长GaN外延层的方法。相比于直接在AlN缓冲层上生长GaN外延层,引入GaN过渡层显著地提高了外延层的晶体质量并降低了外延层的裂纹密度。使用X射线双晶衍射仪、光学显微镜以及在位监测曲线分析了GaN过渡层对外延层的晶体质量以及裂纹密度的影响。实验发现,直接在AlN缓冲层上生长外延层,晶体质量较差, X射线(0002)面半高宽最优值为0.686°,引入GaN过渡层后,通过调整生长条件,控制岛的长大与合并的过程,从而控制三维生长到二维生长过渡的过程,外延层的晶体质量明显提高, (0002)面半高宽降低为0.206°,并且裂纹明显减少。研究结果证明,通过生长合适厚度的GaN过渡层,可以得到高质量、无裂纹的GaN外延层。     

采用AlN缓冲层在Si(111)衬底上生长GaN的形貌

针对Si衬底上生长GaN具有的特有形貌进行了研究,分析采用扫描电镜(SEM)、X射线能谱仪(EDS)、原子力显微镜(AFM)等手段,研究了使用AlN作为缓冲层的GaN的生长模式、缺陷形成机理、应力释放机制.并且发现缓冲层厚度和外延层生长温度对裂纹和表面缺陷的形成有很大的影响.     

采用AlN缓冲层在Si(111)衬底上生长GaN的形貌

针对Si衬底上生长GaN具有的特有形貌进行了研究,分析采用扫描电镜(SEM)、X射线能谱仪(EDS)、原子力显微镜(AFM)等手段,研究了使用AlN作为缓冲层的GaN的生长模式、缺陷形成机理、应力释放机制.并且发现缓冲层厚度和外延层生长温度对裂纹和表面缺陷的形成有很大的影响.     

SiC衬底AlN缓冲层的应变对GaN外延层质量的影响

在3英寸(1英寸=2.54 cm)SiC衬底上采用金属有机物化学气相沉积(MOCVD)法生长GaN外延材料。研究了AlN缓冲层的应变状态对GaN外延层应变状态和质量的影响。使用原子力显微镜和高分辨率X射线双晶衍射仪观察样品表面形貌,表征外延材料质量的变化,使用高分辨喇曼光谱仪观察外延材料应力的变化,提出了基于外延生长的应变变化模型。实验表明,GaN外延层的张应变随着AlN缓冲层应变状态的由压变张逐渐减小,随着GaN张应力的逐渐减小,GaN位错密度也大大减少,表面形貌也逐渐变好。     

100mm直径硅衬底上MOCVD外延生长无裂纹GaN

为实现在100 mm直径硅衬底上金属有机物化学气相外延(MOCVD)生长无裂纹GaN,系统研究了预铺铝时间参数对AlN成核质量的影响、不同厚度条件下AlN层对GaN生长的影响以及Al组分渐变的AlGaN缓冲层对GaN裂纹抑制的效果。实验结果表明,适当的预铺铝时间可以显著提高AlN成核层晶体质量,合理的AlN层厚度有助于上层GaN的生长,AlN与GaN之间AlGaN缓冲层的引入可以有效抑制GaN裂纹的产生。最后,采用高分辨率X射线衍射(HRXRD)测试了MOCVD外延生长的无裂纹GaN材料,得到AlN(002)面、GaN(002)面和GaN(102)面的衍射峰半峰宽(FWHM)分别为1 382,550和746 arcsec。     

Characteristics of GaN grown on 6H-SiC with different AlN buffers

Characteristics of GaN grown on 6H-SiC (0001) substrates using different thicknesses of AlN buffers are studied. It is found that the surface morphology and crystal quality of GaN film closely depends on the strain state of the AlN buffer. For a thicker AlN buffer, there are cracks on GaN surface, which make the GaN films unsuitable for applications. While for a thinner AlN buffer, more dislocations are produced in the GaN film, which deteriorates the performance of GaN. Possible generation mechanisms of cracks and more dislocations are investigated and a ～100 nm AlN buffer is suggested to be a better choice for high quality GaN on SiC.     

Investigations of GaN growth on the sapphire substrate by MOCVD method with different AlN buffer deposition temperatures

The effects of different AlN buffer deposition temperatures on the GaN material properties grown on sapphire substrate was investigated. At relatively higher AlN buffer growth temperature, the surface morphology of subsequent grown GaN layer was decorated with island-like structure and revealed the mixed-polarity characteristics. In addition, the density of screw TD and leakage current in the GaN film was also increased. The occurrence of mixed-polarity GaN material result could be from unintentional nitridation of the sapphire substrate by ammonia (NH₃) precursor at the beginning of the AlN buffer layer growth. By using two-step temperature growth process for the buffer layer, the unintentional nitridation could be effectively suppressed. The GaN film grown on this buffer layer exhibited a smooth surface, single polarity, high crystalline quality and high resistivity. AlGaN/GaN high electron-mobility transistor (HEMT) devices were also successfully fabricated by using the two-step AlN buffer layer.     

溅射AlN技术对GaN基LED性能的影响

研究了在图形蓝宝石衬底(PSS)上利用磁控溅射制备AlN薄膜的相关技术,随后通过采用金属有机化学气相沉积(MOCVD)在相关AlN薄膜上生了长GaN基LED.通过一系列对比实验,分析了AlN薄膜的制备条件对GaN外延层晶体质量的影响,研究了AlN薄膜溅射前N2预处理功率和溅射后热处理温度对GaN基LED性能的作用机制.实验结果表明:AlN薄膜厚度的增加,导致GaN缓冲层成核密度逐渐升高和GaN外延膜螺位错密度降低刃位错密度升高;N2处理功率的提升会加剧衬底表面晶格损伤,在GaN外延膜引入更多的螺位错;AlN热处理温度的升高粗化了表面并提高了GaN成核密度,使得GaN外延膜螺位错密度降低刃位错密度升高;而这些GaN外延膜位错密度的变化又进一步影响到LED的光电特性.     

GaN薄膜表面形貌与AlN成核层生长参数的关系

采用金属有机物化学气相淀积技术生长了以AlN为成核层的GaN薄膜,研究了成核层生长时三甲基铝(TMAl)流量对最终GaN薄膜表面形貌的影响.研究结果表明,高质量GaN薄膜只能在高TMAl流量下获得,采用充足的TMAl源才能形成满足需要的AlN成核点,这是生长高质量GaN薄膜的一个先决条件.     

Effect of AlN buffer layer thickness on the properties of GaN films grown by pulsed laser deposition

The GaN films are grown by pulsed laser deposition (PLD) on sapphire, AlN(30 nm)/Al₂O₃ and AlN(150 nm)/Al₂O₃, respectively. The effect of AlN buffer layer thickness on the properties of GaN films grown by PLD is investigated systematically. The characterizations reveal that as AlN buffer layer thickness increases, the surface root-mean-square (RMS) roughness of GaN film decreases from 11.5 nm to 2.3 nm, while the FWHM value of GaN film rises up from 20.28 arcmin to 84.6 arcmin and then drops to 31.8 arcmin. These results are different from the GaN films deposited by metal organic chemical vapor deposition (MOCVD) with AlN buffer layers, which shows the improvement of crystalline qualities and surface morphologies with the thickening of AlN buffer layer. The mechanism of the effect of AlN buffer layer on the growth of GaN films by PLD is hence proposed.     

Effect of AlN buffer thickness on GaN epilayer grown on Si(1 1 1)

We studied the influence of high temperature AlN buffer thickness on the property of GaN film on Si (1 1 1) substrate. Samples were grown by metal organic chemical vapor deposition. Optical microscopy, atomic force microscopy and X-ray diffraction were employed to characterize the samples. The results demonstrated that thickness of high temperature AlN buffer prominently influenced the morphology and the crystal quality of GaN epilayer. The optimized thickness of the AlN buffer is found to be about 150 nm. Under the optimized thickness, the largest crack-free range of GaN film is 10 mm×10 mm and the full width at half maximum of GaN (0 0 0 2) rocking curve peak is 621.7 arcsec. Using high temperature AlN/AlGaN multibuffer combined with AlN/GaN superlattices interlayer we have obtained 2 μm crack-free GaN epilayer on 2 in Si (1 1 1) substrates.     

硅衬底GaN基LED外延生长的研究

采用在AlN缓冲层后原位沉积SiN掩膜层,然后横向外延生长GaN薄膜.通过该法在硅衬底上获得了1.7 μm无裂纹的GaN薄膜,并在此基础上外延生长出了GaN基发光二极管(LED)外延片,其外延片的总厚度约为1.9 μm.采用高分辨率双晶X-射线衍射(DCXRD)、原子力显微镜(AFM)测试分析.结果表明,GaN薄膜(0002)面的半峰全宽(FWHM)降低到403 arcsec,其表面平整度得到了很大的改善;InGaN/GaN多量子阱的界面较平整,结晶质量良好.光致发光谱表明,GaN基LED峰值波长为469.2 nm.     

间歇供氨高温AlN缓冲层对AlGaN/GaN异质结的影响

研究了以间歇供氨的方法直接高温生长的氮化铝为缓冲层的AlGaN/GaN材料,高温氮化铝的应用可以有效的提高晶体质量和表面形貌,并且二维电子气的浓度和迁移率也得到改善。