InGaAs/GaAs异质结材料的MOCVD生长及性质研究

	InGaAs/GaAs异质结材料的MOCVD生长及性质研究
	韩智明
学位类型	硕士
导师	缪国庆
	2014-11
学位授予单位	中国科学院大学
学位专业	凝聚态物理
关键词	金属有机化合物化学气相淀积两步生长法铟镓砷砷化镓缓冲层
摘要	InGaAs/GaAs失配异质结材料有较高的电子迁移率、材料稳定性好，并且带隙在一定范围内(0.36-1.42eV)可调等优点，在光电子器件领域有着十分广阔的应用前景。GaAs基InGaAs红外探测器在短波方向上截止波长更短，在焦平面阵列的应用上具有很多优点。因此，生长高质量的InGaAs/GaAs失配异质结材料对InGaAs红外探测器阵列的研制和发展有非常重要的意义。InxGa1-xAs与GaAs衬底的晶格失配较大，较大的晶格失配使我们难以得到高质量的外延材料。为了解决晶格失配问题人们研究了很多方法，目前在外延层与衬底之间引入缓冲层是解决晶格失配的有效方法。其中两步生长法已经成为外延生长中解决晶格失配最常用、最有效的方法之一。两步生长法是指在生长外延层之前，先在衬底上低温生长一层组分固定的缓冲层，退火后在高温条件下生长外延层。低温生长的缓冲层为后续高温生长的外延层提供取向成核中心，成为外延层的模板，有效的抑制位错生长，使外延层按2D生长模式生长，从而改善外延层质量。本文利用MOCVD技术，首次采用两步生长法在GaAs衬底上外延生长InGaAs材料，探索了两步生长法外延生长InGaAs/GaAs异质结材料的可行性并研究了两步生长法中缓冲层厚度对外延材料质量的影响。验证了两步生长法可以有效的降低位错密度、改善外延层质量，为今后研制GaAs基InGaAs红外探测器奠定了材料基础。通过扫描电子显微镜、原子力显微镜、X射线衍射、拉曼散射光谱、电化学腐蚀及透射电子显微镜对材料进行表征，重点研究了缓冲层厚度对外延层表面形貌、表面粗糙度、结晶质量、合金有序度、应力、本征载流子浓度、位错的形貌及位错密度的影响。得到以下结论： 1. 利用扫描电子显微镜与原子力显微镜研究了缓冲层厚度对外延层表面形貌及表面粗糙度的影响。结果表明，当缓冲层超过一定厚度后，样品表面形貌明显改善，粗糙度下降，随着缓冲层厚度的增加，表面形貌无明显变化，粗糙度小幅度增加。 2. 利用X射线衍射、拉曼散射及电化学腐蚀研究了缓冲层厚度对外延层结晶质量、位错密度、合金有序度、应力及载流子浓度的影响。结果表明，缓冲层厚度存在最优值，越接近最优值，外延层结晶质量越好、位错密度越少、结晶有序度越高、应力越小、本征载流子浓度越小。 3. 利用透射电子显微镜研究了缓冲层厚度对样品截面位错形貌及外延层位错密度的影响。结果表明，位错在缓冲层及外延层中的分布是随机的，一定厚度的缓冲层可以有效释放应力、抑制失配位错的生长，将位错阶段在缓冲层与外延层界面处，降低外延层位错密度；过薄的缓冲层无法有效的抑制位错的生长，大量的位错穿过缓冲层向外延层表面延伸；过厚的缓冲层虽然对失配位错有抑制作用，但外延层会产生大量的位错，使外延层质量下降。
其他摘要	InxGa1-xAs/GaAs heterojunction materials has many advantages such as high absorption coefficient, high mobility, good uniformity and stability comparing with conventional material and has wide applications in photoelectric devices. InGaAs detectors with GaAs substrate possess shorter wavelength and have advantages in focal plane arrays. Therefore, there is considerable significance to get high quality InGaAs/GaAs. High quality InGaAs/GaAs could not be easily got because of the lattice mismatch. Two-step growth was one of the most effective methods in solving the mismatch, just as its name implies, the buffer layer with different growth conditions is deposited first, after the anneal, epitaxial layer is grown subsequently. Buffer layer provide nucleation centers for epitaxial layer growth as a template and suppress the dislocations, therefore epitaxial layer growth exhibits 2-D growth mode and the quality of epitaxial layer was improved. In this paper, InGaAs was deposited on GaAs substrate through two-step growth by MOCVD for the first time. Effect of buffer layer thickness on quality of epitaxial layer has been studied, and the method of two-step growth to reduce dislocation density was verified. The research provides a solid foundation for the following infrared detector. The heterostructure InGaAs/GaAs was investigated by scanning electron microscopy, atomic force microscopy, X-ray diffraction, Raman scattering spectroscopy, Electrochemical C-V Profiler and transmission electron microscopy. The effect of buffer layer thickness on epitaxial layer morphology, surface roughness, crystalline quality, alloy degree of order, the strain, intrinsic carrier concentration and dislocation density was studied. SEM and AFM was adopted to investigate the effect of buffer layer thickness on surface morphology and surface roughness. The results indicated that epitaxial layer surface morphology was improved when the buffer layer thickness exceeds a certain thickness, and the epitaxial layer surface morphology has no obvious changes when the buffer layer thickness continues to increase. XRD, Raman spectra and ECV was used to investigate the effect of buffer layer thickness on epitaxial layer quality, dislocation density, alloy degree of order, the strain and carrier concentration. It was indicated that there exist an optimal buffer layer thickness to get an epitaxial layer with excellent crystalline quality. The influence of buffer layer thickness on dislocation density and morphology of epitaxial layer was studied. The results showed that dislocations distribute randomly in buffer layer and epitaxial layer. Certain thickness buffer layer was effective in strain relaxation and suppression of dislocations. The faults and dislocations was restricted in interface to reduce the density. It is useless to suppress the dislocations if buffer layer was too thin, then the dislocations will propagate to the surface from buffer layer. Although thick buffer layer is effective for suppression of dislocations, lots of dislocations will generate in the interface and upward to the epitaxial layer even to the surface. And the quality of epitaxial layer will decline.
语种	中文
文献类型	学位论文
条目标识符	http://ir.ciomp.ac.cn/handle/181722/44653
专题	中科院长春光机所知识产出
推荐引用方式 GB/T 7714	韩智明. InGaAs/GaAs异质结材料的MOCVD生长及性质研究[D]. 中国科学院大学,2014.

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