May 21st, 2015

The most commonly used Hall Effect devices are fabricated with Silicon. The important figure of merits of Hall sensors are voltage and current - related sensitivities. These sensitivities depend on the device materials electronic properties such as charge carrier mobility and density. However, for futuristic advanced applications requires higher sensitivity Hall sensors. The other well-known materials are based on high purity III/V semiconductors like GaAs or InAs based heterostructures. Though lot of efforts has been gone in developing sensors using these materials, sensitivity values are restricted.
Now the researchers from Germany at RWTH University and AMO GmbH Aachen have fabricated ultra-high sensitive Hall Effect sensors using single layer graphene. The results are published in Applied Physics Letters. Graphene, two dimensional atomic form of carbon, is a potential candidate for highly-sensitive Hall sensors because of its very high carrier mobility at room temperature and very low carrier densities. These properties make graphene a material that can outperform all currently existing Hall sensor technologies.
Researchers have protected the graphene from ambient contaminations by encapsulating it with hexagonal boron nitride layers; another highly promising 2D insulating material. The fabricated devices show a voltage and current normalized sensitivity of up to 3 V/VT and 5700 V/AT, respectively. These values are more than one order of magnitude above the values achieved in Silicon based and a factor of two above the values achieved with the best III/V semiconductors Hall sensors in ambient conditions. In addition, these results are far better than the earlier reported graphene Hall sensors on Silicon oxide and Silicon carbide substrates.
This new sensitivity level will enable devices with higher precision, lower energy consumption with smaller dimensions. This work will show new light for using graphene in more commercial applications, as Hall sensors are integral part of many household appliances. The research work is supported by the EU Graphene Flagship project (Contract No. NECT-ICT-604391) and the ERC (GA-Nr. 280140).