High Temperature Graphene Sensors for Harsh Environment Current Sensing

Abstract

Graphene Hall effect sensors with low thermal drift suitable for the real time monitoring of current in a power electronic module for aerospace applications are demonstrated operating at temperatures up to 500 K. The change in critical electronic properties with increasing temperature, particularly sheet carrier concentration and carrier mobility, are shown with parameters found to be uniquely influenced by the Dirac point of the graphene layer used to realise the sensor. The sheet carrier concentration is shown to go through a maximum of 1.91×10 ¹³ cm ^-2 , coincident with the mobility minimum of 1.30×10 ³ cm ² V ^-1 s ^-1 at 373 K. This effect results in a non- monotonic behaviour of the sensitivity of the Hall device, however this can be mitigated by means of control of the sheet carrier concentration by means of gating. Omitting the deviation of the characteristics resulting from the influence of the Dirac point, the thermal coefficient of the sensitivity is found to be 921ppm/K, a significant reduction on commercially available Hall elements. This indicates that optimization of graphene Hall sensors using gating can realise high sensitivity Hall effect measurements with a low temperature coefficient.