Berlin 2018 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 55: Quantum dots and wires: Preparation and characterization

HL 55.4: Vortrag

Freitag, 16. März 2018, 10:15–10:30, A 151

Axial Ga(As,Bi) insertions in GaAs nanowires grown by molecular beam epitaxy — •Miriam Oliva, Ryan B. Lewis, Guanhui Gao, Esperanza Luna, Manfred Ramsteiner, Chiara Sinito, Oliver Brandt, Uwe Jahn, and Lutz Geelhaar — Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, 10117 Berlin

The Ga(As,Bi) semiconductor alloy is promising for infrared optoelectronics, allowing all bandgaps below that of GaAs to be reached in principle. Growth of Ga(As,Bi) by molecular beam epitaxy requires very low growth temperatures (220–330C) and Ga-rich environments [R. B. Lewis et al.; Appl. Phys. Lett. 101, 082112 (2012)]. These requirements often result in Ga droplets on the Ga(As,Bi) surface, which are detrimental for optoelectronic applications. Here we show that the Ga droplets atop Ga-assisted GaAs nanowires provide an ideal environment for the growth of Ga(As,Bi), and we develop a novel growth procedure to realize axial Ga(As,Bi) insertions in GaAs nanowires. First, we enrich the Ga droplets with Bi, resulting in a Bi/Ga-volume ratio of around 8. We then expose these droplets to an As2 flux, precipitating a Ga(As,Bi) segment from the liquid droplet. Finally, excess Bi that did not incorporate into Ga(As,Bi) can be desorbed. We explore the dependence of the Bi content on the substrate temperature during growth. Transmission electron microscopy reveals uniform Ga(As,Bi) segments, with a Bi content of about 17% for segments formed at 300C. These results open the door to infrared optoelectronic devices based on GaAs/Ga(As,Bi) axial nanowire heterostructures.

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