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 AlsoHigh-entropy alloys (HEAs), which are formed by combining nearly equal parts of several – usually five or more – primary metals, are an emerging class of advanced materials that hold great potential for creating materials with superior mechanical, thermal, and catalytic properties. Another attraction of HEAs is that they can create effective alternatives to materials that are scarce, hazardous, expensive, or subject to international restrictions or conflict.
Read moreResearchers at Johannes Gutenberg University Mainz (JGU) are pursuing a completely new and unconventional strategy to improve the way data can be processed and – in particular – stored. Together with their partners at the Hebrew University of Jerusalem, they have been granted funding by the Carl Zeiss Foundation (CZS). The project of this interdisciplinary team is among a total of five projects – all at early stages and considered to be especially innovative – to be funded through the new CZS Wildcard program. The team members, based in Mainz and Jerusalem, have come up with the idea of bringing together two different forms of chirality to develop new data storage systems that are faster, smaller, and more efficient than those currently available.
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