Separated terminal 2D hall sensors with improved sensitivity

Official URL: https://dx.doi.org/10.1016/j.sna.2021.112550

This paper studies Hall effect sensor current-related sensitivity in terms of its dependence on electrode design, usage of 2D materials and sensor geometry. The sensors are constructed on silicon wafers with 2D substrates such as graphene and hBN-graphene heterostructures. To obtain shaped sensors 2D layers are etched using e-beam lithography and oxygen plasma etching. Subsequently chromium and gold layers are coated and patterned by e-beam lithography and deposition, respectively. For both sensors, only graphene is patterned. A separate electrode scheme is implemented to improve the current-related Hall sensitivity. Furthermore, sensitivities between cross-shaped and octagonal-shaped sensors are compared. The current-related Hall sensitivity SI was measured between octagonal and cross-shaped sensors FEM current conduction analysis based simulations are used to simulate bias current distribution within the sensors. A “current retainment factor” was defined to indicate the effective bias current in various sensor geometries. The change in this factor closely follows current-related sensitivity change between different sensor geometries. For cross-shaped sensors, the sensitivity difference between separated-electrode and combined-electrode sensors is as much as 2–5%. However, the octagon-shaped sensors exhibit as much as 25–35% sensitivity change between versions utilizing separated and combined electrodes. Similar differences are valid for sensors built on graphene as well as hBN-graphene heterostructures. The sensitivity increase when using separated electrodes is attributed to increased current retainment factors and effective bias currents. Simulations that compute these factor can accurately predict geometry dependence of Hall effect sensors.