Modeling and characterizing power semiconductors at low temperatures

The application of power semiconductors at cryogenic temperatures has recently gained significance in protection elements of SMES (superconducting magnetic energy storage) operating at LHT (liquid helium temperature). The evolution of HT (high temperature)-superconductors, however, is still proceeding and will provide in the near future magnetic insensitive materials operating at LNT (liquid nitrogen temperature). Due to the low price of LN, it will then make sense to reconsider the additional cooling of power electronic topologies and, consequently, to take advantage of improving characteristics of power semiconductors with decreasing temperature. One objective of this paper is to characterize the temperature dependence of different devices' static and dynamic behaviour both by measurement and physical analysis by means of recently published circuit models. Secondly physical assumptions in these models are validated, proving their capability to act as the circuit and device designer's right hand.