The surge current rating of a thyristor increases as the width of the pulse decreases. For a single non-repetitive pulse, it's not uncommon for a thyristor to have a surge rating that is 10x or even 100x higher than its average or RMS current rating.
For example, a TYN640 thyristor has an average current rating of 25 A for a half-cycle sinusoidal current. However, when the width of this current is decreased to just 10 milliseconds, the absolute maximum surge rating increases to 480 A. For a 1-millisecond pulse, 1500 A. And for a 200-microsecond pulse, 2500 A.
Eventually, the surge rating starts decreasing again after shorter pulses start hitting the di/dt limitation of the thyristor. But in general, the shorter the pulse, the higher the surge current. This property makes thyristors extremely useful in pulse and surge generators.
However, the surge ratings of MOSFETs do not have this property.
For nearly all MOSFETs, the pulsed drain current is given as a single number in the datasheet, and it's not a function of the pulse width. Instead, "pulse width tp limited by Tjmax". In other words, the pulse width is determined by temperature rise, but it must always be lower than the fixed pulsed rating.
As far as I'm aware of, MOSFETs are rated this way regardless of their voltage rating, Rds(on), packaging, silicon or SiC. But I'm open to correction if anyone can find an example to the contrary.
For example, using the IPB65R050CFD7A MOSFET, although the 211 A pulsed rating is significantly higher than the 45 A DC rating (with an infinite heat sink), but it cannot be increased further by reducing the pulse width.
The Safe Operating Area shows that 200 A is the upper limit under any circumstances.
The surge current ratings of IGBTs are similar to MOSFETs. Using the STGW75M65DF2 as an example - its DC current rating is 120 A, but the pulsed rating is only 225 A, and again, "pulse width limited by maximum junction temperature".
As far as I'm aware of, nearly all IGBTs are rated this way regardless of their voltage rating or packaging.
Again, the Safe Operating Area shows the surge current is maxed out around 200 A.
I believe localized hotspot formation in the silicon set the ultimate limitation of surge current rating of all semiconductor switches, as heating under a short pulse is an adiabatic condition. I know this is the physical origin of the di/dt limitation of thyristor, and I guess it's also why MOSFETs and IGBTs have a maximum pulsed current rating.
But why does the hotspot create only a di/dt limitation in thyristors, but a pulsed current limitation in MOSFETs and IGBTs? Why does thyristor's surge current rating keep increasing with decreasing pulse width, but MOSFET or IGBT's surge current rating stop increasing with decreasing pulse width beyond a point? What is the basis in semiconductor physics behind setting a static pulsed rating regardless of its width for MOSFETs and IGBTs?