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

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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.