Growth of SiGe bulk single crystals with low defect density and creation of functional heterostructures

本研究的目的是实现硅锗块体晶体具有均匀的成分和低缺陷密度的衬底具有灵活的选择晶格常数和带隙，因为这些提供了机会，探索新的材料研究时，结合先进的异质外延方法制备异质结构与控制应变和/或带不连续的组成材料。通过界面温度的在线监测系统、提拉速率的动态控制、籽晶取向的优化等一系列改进措施，建立了一套获得高质量SiGe体晶的晶体生长技术。该方法也适用于其它具有完全溶解性的多组分半导体，InGaAs块体晶体的实现证明了这一点。另外，浮区生长技术有利于实现低缺陷密度的SiGe体晶，在国产SiGe体衬底上实现了结构完整性较SiGe虚拟衬底上有较大提高的应变Si薄膜。此外，在应变Si薄膜中实现了高电子迁移率的二维电子异质结、高峰谷电流比的共振隧穿二极管、应变量子威尔斯阱的强发光等功能，并利用晶格锁存效应在InGaAs衬底上成功生长了立方对称的In、N含量较好的InGaAsN。生长的0.2 μ m厚InGaAsN薄膜在1.3-1.55 μm范围内显示出光致发光。这些结果表明，多组分半导体衬底可用于各种材料的研究，因为我们的晶体生长技术可以应用于各种多组分晶体的任意组成，在液态和固态下都具有完全的溶解度。

The purpose of this research is to realize SiGe bulk crystals with uniform composition and low defect density for substrates with a flexible choice in lattice constants and bandgaps since those offer opportunities to explore novel materials research when combined with an advanced heteroepitaxy method to prepare heterostructures with controlled stain and/or band discontinuity in constituent materials. By integration of a series of improvements such as the in-situ monitoring system of the interface temperature, the dynamical control of the pulling rate, the optimization of the seed orientation, we established a crystal growth technique to obtain high-quality SiGe bulk crystals. The method was revealed to be applicable other multicomponent semiconductors with complete solubility as demonstrated by realization of InGaAs bulk crystal. In addition, floating zone growth was shown to be useful to realize SiGe bulk crystal with low defect density.On homemade SiGe bulk substrates, we realized strained Si thin film with improved structural perfection compared with that on SiGe virtual substrate. Furthermore, various functional heterostructures have been achieved such as two-dimensional electron with high electron mobility in strained Si thin film, resonant tunneling diodes with high peak-to-valley current ratio, intense photoluminescence from strained quantum wells and so on. On bulk InGaAs substrates, InGaAsN with cubic symmetry and desirable In and N contents were grown successfully owing to the lattice-latching effect. As-grown 0.2-μm-thick InGaAsN films exhibited photoluminescence in the range of 1.3-1.55 μm.These results demonstrate that multicomponent semiconductor bulk substrates are available for various materials research since our crystal growth technique can be applied to arbitrary compositions of various multicomponent crystals with complete solubility in both the liquid and solid states.