High Spin Hall Angle doped BiSbX Topological Insulators using novel high resistive growth and migration barrier layers

Abstract

We have fabricated simple bottom-SOT film stacks using doped BiSbX TI materials as the SOT layer with novel high resistance nucleation/growth and migration barrier layers. The thin buffer layer produces a very strong fiber axis (012) texture (rocking curve ~ 7 degs. FWHM). The migration barrier between the FM and The SOT layers significantly reduces both Bi,Sb migration out of the SOT and electrical shunting across the FM. The seed and capping layers have high resistivities (~ 250 uohm-cm), as do the thin migration and nucleation/growth layers (resistivities ~ > 300 uohm-cm). The migration barrier layer is critical to reduce intermixing between SOT and FM layer reducing SOT surface roughness, sharpening the SOT-interlayer interface, and to reduce FM shunting effects. Cross Hall-bar patterns 20umX60um (WxL) were fabricated from the simple film stacks shown schematically in figure 1. Very high SHA values of about 24 (see figs. 4b., and 5b.) were measured on two differently doped BiSbX SOT materials.