Modulation Doping of Template-Defined InGaAs Nanowires

Templated semiconductor nanowires with strong Rashba spin-orbit interaction are a great platform to create and study novel quantum states of matter, such as helical states and spin helices, Majorana- and para-fermions. Here, we report recent results on templated InGaAs nanowire Y-junctions grown on GaAs nanomembranes^[1] with modulation doping. Modulation doping has been successfully used in many high-performance systems to create structures with enhanced mobility and higher carrier concentrations. We investigate modulation doping in GaAs nanomembranes grown via molecular beam epitaxy in a selective area growth approach. In a novel process, the dopants migrate up through the GaAs membrane during growth. This remote doping process has enabled major improvements in notable system parameters such as mean free path, coherence length, and spin-orbit length. With a top gate, we can tune between weak localization and antilocalization. The improvements suggest ballistic transport may be within reach. Further, experiments with superconducting contacts for proximitizing and Majorana zero modes can be envisioned.

[1] M. Friedl et al., Nano Lett. 18, 2666-2671 (2018)