大失配InGaAs异质结的MOCVD生长与材料特性研究

发布时间：2018-01-30 14:16

本文关键词： InGaAs 晶格失配两步生长法低温缓冲层界面位错失配应力释放异质结带阶结构　出处：《中国科学院长春光学精密机械与物理研究所》2017年博士论文　论文类型：学位论文

【摘要】：In GaAs是1-3μm近红外波段重要的探测材料。高In组分的InxGa_(1-x)As(x0.53)由于没有同质衬底,在生长中则会出现晶格失配,使外延层质量变差。晶格失配一直是半导体材料异质外延中存在的主要问题,缓冲层是一种很有效的方法,它释放了异质结中的失配应力。各类缓冲层的应用在很大程度上解决了一些异质外延中的晶格失配问题,获得了良好晶体质量的外延层材料。尽管缓冲层已经被研究和使用了很长时间,但是目前仍然没有一个完整的关于缓冲层作用机理或模型被提出,理论的缺失使我们无法进一步深入、有目的地去优化和设计缓冲层结构,无法对材料的异质外延生长作出更有效的改进。本论文针对高In组分InGaAs材料外延中存在的晶格失配问题,采用两步生长法,引入低温缓冲层,在Ga As衬底上成功生长了良好晶体质量的In_0.78Ga_0.22As外延层,并对低温缓冲层以及界面位错作了深入的分析和研究,取得了以下主要研究成果:1、采用两步生长法,利用MOCVD技术在GaAs衬底上生长了高In组分的In_0.78Ga_0.22As外延层,实验结果表明,低温缓冲层可以有效解决晶格失配,而且,不同厚度下,低温缓冲层对失配应力释放的程度也存在差异:适当厚度的低温缓冲层可以有效解决晶格失配,使失配应力得到很好的释放,从而带来具有良好晶体质量的外延层;除此之外,适当厚度的低温缓冲层也可以有效抑制和减少位错,从而降低外延层的位错密度。多种研究和表征手段表明,适当厚度的低温缓冲层是解决晶格失配、有效释放应力以及获得良好外延层晶体质量的关键。2、利用高分辨TEM对In_0.78Ga_0.22As/GaAs失配异质结作了深入的研究和分析。从低温下缓冲层的岛状生长入手,以厚度为变化,研究了界面位错与缓冲层厚度、失配应力释放的关系,并提出了低温缓冲层降低位错密度的作用机理。我们认为:不同厚度低温缓冲层下不同的应力释放程度要直接归因于In_0.78Ga_0.22As/GaAs失配异质结界面位错的类型和排布,周期性极好的90°位错排列对于失配应力释放是最为有效的。低温缓冲层岛状生长中每个阶段小岛之间闭合掩埋的状态直接决定了失配应力的释放,位错行为的变化带来应力释放的变化。低温缓冲层以及界面位错的机理分析与研究给予了我们优化和控制缓冲层的大概方向和思路,从而达到对异质结中失配应力的调控,实现高质量In GaAs失配材料的外延生长。3、使用XPS和UPS对In_0.82Ga_0.18As/InP失配异质结的界面带阶结构排布进行了测定,得到其价带带阶为0.413 eV,由此推出其导带带阶为0.457 eV,并分别从实验和理论方面验证了该结果的准确性。最终得出In_0.82Ga_0.18As/InP异质结界面表现出一个type-I型straddling带阶结构。In_0.82Ga_0.18As/InP异质结带阶结构的确认具有重要意义,能带调控给予了我们控制载流子输运过程的可能性,从而为实现异质结器件结构及功能的多样化和创新奠定了理论基础。
[Abstract]:In GaAs is an important material for detection of 1-3 m near infrared band. High In component InxGa_ (1-x) As (x0.53) because there is no homogeneous substrate, growth appears lattice mismatch, the quality of epitaxial layer becomes worse. The lattice mismatch exists in heteroepitaxial semiconductor materials the main problem and the buffer layer is a very effective method, it releases the heterojunction mismatch stress. Application of buffer layer to a great extent to solve some of the heteroepitaxial lattice mismatch problem, obtained the good crystal quality of the epitaxial material. Although the buffer layer has been studied and used. For a long time, but there is not a complete on the buffer layer mechanism or model is put forward, the lack of theory make it impossible for us to go further, the design and optimization of buffer layer structure, not on heteroepitaxial growth of the material to make more effective The improvement in this paper. The high In component of InGaAs epitaxial materials in the lattice mismatch problem, using two step growth method, the introduction of low temperature buffer layer, In_0.78Ga_0.22As layer growing good crystal quality in Ga on the As substrate, and the low temperature buffer layer and interfacial dislocations were in-depth analysis and study. The main results are as follows: 1, using two step growth method on GaAs substrates of In_0.78Ga_0.22As epitaxial layer with high In component by using MOCVD technique, the experimental results show that the low temperature buffer layer can effectively solve the lattice mismatch, and different thickness, there are also differences on the mismatch stress release the degree of low temperature buffer layer: low-temperature buffer layer thickness can effectively solve the lattice mismatch, the mismatch stress is to be a good release, resulting in epitaxial layer has good crystal quality; in addition, the proper thickness of the low temperature The buffer layer can also effectively inhibit and reduce dislocation, thereby reducing the dislocation density of epitaxial layer. Show a variety of research and characterization of low temperature buffer layer thickness is to solve the problem of lattice mismatch, effective stress release and key.2 to obtain good epitaxial crystal quality, TEM made a thorough research and analysis of In_0.78Ga_0.22As/GaAs mismatch heterojunction with high resolution. The growth starting from the low temperature buffer layer of the island, with the thickness change, interface dislocation and buffer layer thickness on the relationship between mismatch stress release, the low temperature buffer layer down low dislocation density and the mechanism proposed. We think that different thickness under different low temperature buffer layer the stress release degree to direct attribution type and arrangement of In_0.78Ga_0.22As/GaAs mismatch heterointerface dislocation, 90 degrees dislocation periodic arrangement for excellent mismatch stress release is the most effective. Low temperature buffer layer between each stage of growth in Island Island closed buried state directly determines the mismatch stress release, change of dislocation behavior due to the change of stress release. Low temperature buffer layer and the mechanism of interface dislocation analysis and research has given us the optimization and control of buffer layer about the direction and ideas, so as to achieve regulation of heterojunction mismatch stress, to achieve high quality epitaxial In GaAs mismatch material growth of.3, XPS and UPS of In_0.82Ga_0.18As/InP mismatch heterostructure interface with order structures were determined by the valence band offset of 0.413 eV, which launched the band with order 0.457 and eV. From the experiment and theory to verify the accuracy of the results. Finally the In_0.82Ga_0.18As/InP heterostructure showed a type-I type straddling band structure of.In_0.82Ga_0.18As/InP heterojunction band offset. The confirmation of the structure is of great importance. The band regulation gives us the possibility of controlling the transport process of carriers, thus laying a theoretical foundation for the diversification and innovation of the structure and function of heterojunction devices.

【学位授予单位】：中国科学院长春光学精密机械与物理研究所
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN215

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