An investigation into the utilisation of power MOSFETs at cryogenic temperatures to achieve ultra-low power losses

The cryogenic behaviour of five 200 V rated HEXFET® MOSFETs between the temperatures of 20 K to 100 K are presented, including the on-state resistances, breakdown voltages and electro-thermal behaviour. The results indicate negative temperature dependent behaviour for the on-state resistances below 70 K and non-ohmic behaviour below 40 K. The physical reasons behind these phenomenon were suggested to be the combined behaviour of temperature dependent electron mobility, carrier freeze-out and electric field assisted thermal ionisation. The classically assumed linear temperature relationship for the breakdown voltages was found to be invalid below 100 K and a better model was suggested. A simple analysis into the utilisation of these power MOSFETs that considers the electro-thermal behaviour was discussed and parallel MOSFETs configuration was suggested to optimised the temperature dependent power loss at cryogenic temperatures.