Layered semiconductor gallium selenide (GaSe) is considered a potential candidate for optoelectronic applications because of its direct band gap. Monocrystalline material is, however, a prerequisite to fully exploit these properties in devices, where one-dimensional nano-objects could be considered as a model system. As a consequence of their large surface-to-volume ratio, nano-objects such as nanoribbons are interesting for photodetection applications. Here, we report the vapor−liquid− solid growth of GaSe nanoribbons by MOCVD on 300 mm silicon substrates. A growth model is proposed on the basis of a comprehensive study of the impact of the growth parameters on the nanoribbon morphology. The nanoribbon microstructure is investigated by HR-STEM and Raman spectroscopy characterizations. HR-STEM and TEM cross-sectional observations coupled with EDX analyses reveal a monocrystalline nanoribbon core covered with a native gallium-oxide shell. Test devices are made by contacting individual nanoribbon. The current versus voltage (I−V) characteristic obtained over a range of temperature (−50 to 100 °C) in the dark and under white light illumination is fitted on the basis of a back-to-back Schottky diode model. A stable and repeatable dynamic photoresponse is measured from the GaSe nanoribbons, with an I ON /I OFF ratio of 17 at room temperature.
We demonstrated the fabrication of a densely packed InAs fins network for nanoelectronic applications. High crystalline quality GaSb/InAs layers have been grown directly on 300 mm nominal (001)-Si substrate. The InAs was then processed by etching step using a lithographic mask based on block copolymer to obtain sub-20nm width fins. This block copolymer has been optimized to selfassemble into lamellar structure with a period of 30nm, standing perpendicular to the substrate thanks to a neutral layer. STEM-HAADF characterization displays vertical sidewalls InAs fins with a width as low as 15nm spaced by almost 10nm. Early electrical characterizations exhibit a current flow through the connected fins.
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