Crystalline zinc blende GaAs has been grown on a trigonal c-plane sapphire substrate by molecular beam epitaxy. The initial stage of GaAs thin film growth has been investigated extensively in this paper. When grown on c-plane sapphire, it takes (111) crystal orientation with twinning as a major problem. Direct growth of GaAs on sapphire results in three-dimensional GaAs islands, almost 50% twin volume, and a weak in-plane correlation with the substrate. Introducing a thin AlAs nucleation layer results in complete wetting of the substrate, better in-plane correlation with the substrate, and reduced twinning to 16%. Further, we investigated the effect of growth temperature, pregrowth sapphire substrate surface treatment, and in-situ annealing on the quality of the GaAs epilayer. We have been able to reduce the twin volume below 2% and an X-ray diffraction rocking curve line width to 223 arcsec. A good quality GaAs on sapphire can result in the implementation of microwave photonic functionality on a photonic chip.
Discover AlsoFor the past several decades, scientists have been experimenting with the potential benefits that nanomaterials, particularly carbon nanotubes, could offer semiconductors. As researchers develop methods to further reduce the size of semiconductor materials, dramatic improvements in the physical and chemical properties of these materials continue to arise. In conclusion, minimizing the size of semiconductor materials has been shown to maximize the performance of semiconductors for their application in a wide range of material applications.
Read moreA Ludwig Cancer Research study has developed a novel nanotechnology that triggers potent therapeutic anti-tumor immune responses and demonstrated its efficacy in mouse models of multiple cancers. Led by Co-director Ralph Weichselbaum, investigator Wenbin Lin and postdoctoral researcher Kaiting Yang at the Ludwig Center at Chicago, the study describes the synthesis, mechanism of action and preclinical assessment of the nanoparticle, which is loaded with a drug that activates a protein central to the efficient induction of anti-cancer immunity.
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