IGBT Modules - Technologies, Driver and Application (Second Edition) - page 63

Fig. 1.42
Layer sequence, electrical fielddistributionof aPT IGBT combinedwith trench
gate (not to scale) and imageof thegate structure
All of this has a positive effect on the charge carrier concentration. As a comparison,
shows the simulated carrier densities of IGBTs with a trench structure and a
planar structure. It is very obvious that the carrier density increases toward theemitter in
Trench IGBTs but reduces in Planar IGBTs. Setting the charge carrier density on the
emitter side is therefore dependent on factors that include the relationship between the
individual cell dimensions of the IGBT and the distances between the cells (also known
as pitch). Thismakes infinite adjustments of the charge carrier concentrations possible.
However, it should be borne in mind that conduction loss is reduced at higher
concentration. On the other hand, having more charge carriers to be removed reduces
the turn-off losses. A flat or only slightly rising distribution for the charge carrier
concentration has proved to be a good compromise between the static and dynamic
losses of aTrench IGBT.
Fig. 1.43
Comparison of charge carrier concentrations of TrenchandPlanar IGBTs
Using the simplified equivalent circuit diagram in
the internal voltage drop of
an IGBT can be described as:
1...,53,54,55,56,57,58,59,60,61,62 64,65,66,67,68,69,70,71,72,73,...548
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