Construction of IGBT
The IGBT combines the input characteristics of a MOSFET with the output characteristics of a BJT, resembling the structure of an N-channel MOSFET and a PNP BJT in Darlington configuration. Additionally, the resistance of the drift region can be integrated. In terms of the IGBT’s structure, there are multiple current paths. The primary path is from the collector to the emitter, involving the sequence: “collector, P+ substrate, N-, P, emitter,” which aligns with the PNP transistor equivalent. There’s also a secondary path: “collector, P+ substrate, N-, P, N+, emitter,” which necessitates the inclusion of another NPN transistor, as illustrated in the figure below.
The IGBT consists of four semiconductor layers arranged to create a PNPN structure. The collector (C) electrode connects to the P layer, while the emitter (E) is positioned between the P and N layers. Construction employs a P+ substrate, with an N- layer atop it is forming PN junction J1. Two P regions are crafted on the N- layer, creating PN junction J2. The gate (G) electrode is positioned within a gap in the middle of the P region. Metal electrodes serve as the emitter and gate, with the emitter directly connected to the N+ region and the gate insulated by a silicon dioxide layer. The P+ layer, referred to as the injector layer, injects holes into the N- layer, while the N- layer itself is called the drift region, with its thickness proportional to voltage-blocking capacity.
The upper P layer is known as the body of the IGBT. The N- layer is designed to establish a current path between the emitter and collector, utilizing a channel formed beneath the influence of the voltage applied to the gate electrode. The N- layer is strategically designed to provide a path for the current to flow between the emitter and collector. This current path is influenced and controlled by the voltage applied to the gate electrode. By varying this voltage, the IGBT can regulate the flow of current through the device, making it an essential component in various power electronics applications.
Construction of IGBT
Insulated Gate Bipolar Transistor
IGBT stands for Insulated Gate Bipolar Transistor. IGBTs find extensive applications in various domains, including household appliances like air conditioners and refrigerators, industrial motors, and automotive main motor controllers. Their utilization of these devices serves to enhance overall energy efficiency. IGBT is also called insulated gates because of the insulated gates the IGFETs have high current gain.
Table of Content
- What is an Insulated Gate Bipolar Transistor?
- Construction
- Working
- Parameters
- IGBT Characteristics
- Advantages
- Disadvantages
- Applications