Super junction MOSFET

The super junction MOSFET is the topic we explain here, the super junction or SJ is a structural design mostly used at power semiconductor devices such as MOSFETs and IGBTs.

In this post, we explain the details about the super junction at MOSFET and listed the difference that happened due to the implementation of the super junction at the MOSFET.

Super junction MOSFET structure

Super junction MOSFET structure
Super junction MOSFET structure

image source = Fuji Electric

The figure shows the conventional MOSFET structure and super junction MOSFET structure.

  • The super junction MOSFET structure means a pillar-shaped p-layer attached to the n-layer.
  • When a depletion layer is formed at n-layer by the VDS voltage.
  • The spreading of the depletion layer is different from conventional MOSFETs.

Working of both MOSFETs

  • At the conventional MOSFETs, the electric field intensity is spread strongly on p and n layers.
  • And the electric field reaches its limit of silicon, then becomes the breakdown voltage.
  • But at the super junction MOSFET or SJ-MOS, they are designed with an n-layer that having lower resistance.
  • This will show its low on-resistance, they will also limit the overall size of the MOSFET with the same performance as the conventional MOSFET.
  • At the time the rated voltage rises, the drift layer becomes thicker and so the ON-state resistance is increased at conventional MOSFET.
  • On the super junction MOSFET, irr is larger and trr is faster than conventional MOSFETs.

                                        irr= reverse current

                                      trr= reverse recovery time

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