Template-defined In(Ga)As Nanowires

Templated semiconductor nanowires with strong spin-orbit interaction (SOI) are a scalable and versatile platform [1] to create and study novel quantum states of matter, such as helical states and spin helices and Majorana fermions. Modulation doping is a well-established technique to enhance mobility and control carrier concentration. Here, we report recent results on In(Ga)As nanowires with remote doping in the GaAs nanomembrane template grown via molecular beam epitaxy in a selective area growth approach [2], improving on a bulk-doping approach. This process gives major improvements in mean free path and SOI, which are illustrated in magnetoconductance measurements revealing weak anti-localization behavior across nanowire Y-junctions. With a wrap-around top gate, the density can be tuned down to full depletion without applying an electric field. However, it would be important to control the Rashba SOI with an electric field, which could be generated with a split gate. To implement this on a tall and thin membrane with large aspect ratio is challenging. Here, we employ multiple angle evaporation combined with atomic layer deposition of dielectric layers of HfO2 to create a split gate wrapped around the membrane and nanowire.