Question

Describe with neat sketch the constructional details of IGBT.

Answer 1

Construction:

Insulated gate bipolar transistor or IGBT, is a solid state devices primarily used as an electronic switch which, as it was developed, came to combine high efficiency and fast switching. The insulated gate bipolar transistor (IGBT) is a three terminal semiconductor device combines the benefits of both MOSFET and BJT. So, an insulated gate bipolar transistor (IGBT) has input impedance like that of a MOSFET and low ON state power loss as in a BJT. It is also called as metal oxide semiconductor insulated gate transistor (MOSIGT) and other name to this device are insulated gate transistor (IGT), conductivity modulated field effect transistor (COMFET). It is similar to that of a double-diffused power MOSFET (DMOS) except for a p+ layer at the bottom. This layer forms the IGBT collector and a pn junction with n-drift region, where conductivity modulation occurs by injecting minority carriers into the drain drift region of the vertical MOSFET. Therefore, the current density is much greater than a power MOSFET and the forward voltage drop is reduced. The p+ substrate, n- drift layer and p+ emitter constitute a BJT with a wide base region and hence small current gain.