Development of multicomponent bulk single crystal with uniform composition by the multicomponent zone-melting method

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In this project, we have tried to establish a technology to grow multicomponent semiconductor bulk crystals with uniform composition, which are expected to lead to the creation of new functional heterostructures by greatly widening the choices of lattice constant and band gap of semiconductor substrates. By utilizing the technology, we have grown SiGe bulk crystals.In Fy1999, we designed new growth system equipped with an in-situ monitoring system of the position and the temperature at the growth interface. The system includes a quartz slit which allows an optical access, and a CCD camera to observe the position of the interface, and a thermoviewer to obtain the temperature distribution. In addition, the information can be used to control the pulling rate of the ampoule for the crystal growth. Therefore, precise control of the growth temperature is possible.The starting materials for the SiGe bulk crystal are a Si single crystal as a source, polycrystalline Ge, and Ge (100) single crys … More tal as a seed. By putting the ampoule in an appropriate temperature gradient, polycrystalline Ge and a top part of Ge single crystal are melted to prepare a growth melt. Then, Si dissolves into Ge melt and Si atoms are carried to the interface, mainly by diffusion originating from the concentration gradient, and also by possible influence of convection. Consequently, the supercooling is formed around the growth interface and a driving force for the growth of SiGe crystal is established.By monitoring the interface position during the growth with fixed ampoule, we obtained the growth rate of the crystal. By pulling down the ampoule balanced with the growth rate, we succeeded in growing SiGe with fixed interface position. The pulling down the ampoule was confirmed not to affect the temperature distribution. In other words, SiGe was grown under fixed growth temperature. In fact, EDX analysis clarified that the composition of the crystal is uniform over 20mm.As a next step, we will apply this technique to various material system, and perform epitaxial growth on our original substrates to create new functional heterostructures. Less