Abstract
InGaAs is a potential candidate for Si replacement in upcoming advanced technological nodes because of its excellent electron transport properties and relatively low interface defect density in dielectric gate stacks. Therefore, integrating InGaAs devices with the established Si platforms is highly important. Using template-assisted selective epitaxy (TASE), InGaAs nanowires can be monolithically integrated with high crystal quality, although the mechanisms of group III incorporation in this ternary material have not been thoroughly investigated. Here we present a detailed study of the compositional variations of InGaAs nanostructures epitaxially grown on Si(111) and Silicon-on-insulator substrates by TASE. We present a combination of XRD data and detailed EELS maps and find that the final Ga/In chemical composition depends strongly on both growth parameters and the growth facet type, leading to complex compositional sub-structures throughout the crystals. We can further conclude that the composition is governed by the facet-dependent chemical reaction rates at low temperature and low V/III ratio, while at higher temperature and V/III ratio, the incorporation is transport limited. In this case we see indications that the transport is a competition between Knudsen flow and surface diffusion.
Highlights
We present an investigation by x-ray diffraction (XRD) and transmission electron microscopy (TEM) of the chemical composition of indium gallium arsenide (InGaAs) nanowires and platelets grown by template-assisted selective epitaxy (TASE)
Arranged vertical arrays InGaAs nanowires were grown at 580 °C and V/III ratio of 40 (figure 1(a)) with varying xvap and their average chemical composition in the solid, xsol, was determined by High resolution XRD (HRXRD), using Vegard’s law and the relative position of the InGaAs (111) reflection peak to the Si (111) substrate peak
To elucidate how the In incorporation behavior changes when chemical reactions are fast and the crystal growth is instead limited by vapor transport phenomena, we investigate InGaAs nanowires grown at a higher temperature of 580 °C as well as at two different V/III ratios
Summary
The ternary semiconducting alloy indium gallium arsenide (InGaAs) has gained significant technological importance in recent years It is an excellent materials choice for photo-detection in the mid-infrared (up to 1.6 μm wavelength for In0.5Ga0.5As) with much lower dark-currents than Ge devices [1]. The key concept of TASE is that heteroepitaxy on the Si substrate starts from a single InGaAs nucleus for each individual device. This is achieved by limiting the exposed Si area to less than 100 × 100 nm, much smaller than the migration length of the growth species on the Si surface. We observe compositional variations that can be explained by a facet-type dependent incorporation of Ga and In at low temperature, and transport limited growth at higher temperature and V/III ratio
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