How are super-junction MOSFETs different from common D-MOS?

The depletion layer spreads differently in N-layer, which determines the limit of the breakdown voltage. SJ-MOS can be designed with N-layers with lower resistivity, allowing for lower on-resistance.

Fig. 1: D-MOS and SJ-MOS construction and electric field
Fig. 1: D-MOS and SJ-MOS construction and electric field

SJ-MOS (we call it DTMOS) forms a columnar P layer (P-pillar layer) on a part of N-layer and alternates P-N layers.
When VDS is applied, the depletion layer spreads over N-layer, which is the drifting layer. However, the spreads differently in the common D-MOS (called π-MOS in our case) and SJ-MOS. (See the electric field intensity diagram. The electric field intensity indicates the state in the depletion layer.)
In D-MOS, the interface between P/N-layers has the highest electric field strength, and breakover (breakdown phenomena) occurs when this part exceeds the limit of the material-silicon. This is the limit of the breakdown voltage. On the other hand, SJ-MOS has uniform electric field strength in N-layers.
As a consequence, SJ-MOS can be designed with lower-resistance N-layers, allowing for lower on-resistance.

Please also refer to FAQ below.

Back to FAQs of SiC MOSFETs / MOSFETs / IGBTs / Bipolar Transistors

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