IGBT Modules - Technologies, Driver and Application (Second Edition) - page 51

Fig. 1.27
The R
in terms of area as a function of the blocking voltage U
for a
standardMOSFETand a superjunctionMOSFET (CoolMOS
C3 family)
Superjunction MOSFETs can now be technically realised up to voltages of
900V. The
fundamental difficulty is in the engineering processwhereby the charge carriers in the p-
and n-doped zones are balanced. If the p-zone is not capable of compensating the high
charge carrier concentration of the n-zone exactly, the desired blocking capability can
no longer be guaranteed. This balancing becomes more difficult as the required
blocking voltage increases.
Superjunction MOSFETs are also called charge compensated MOSFETs, due to the
principle of charge carrier compensation.
Fig. 1.28
Layer sequenceof a superjunctionMOSFET (not to scale)
1.5 Insulatedgatebipolar transistors (IGBTs)
As shown in chapter
the npn and pnp structure of bipolar junction transistors
means that they have bothmajority andminority carriers available during the conductive
phase. The internal voltage drop of a bipolar transistor when it is turned on is therefore
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