MOSFET vs IGBT: Understanding Key Differences and Applications

This article compares MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors), highlighting their differences and providing a table to aid in selecting the appropriate device for a given application.

What is a MOSFET?

MOSFET stands for Metal Oxide Semiconductor Field Effect Transistor. There are two main types of MOSFETs: n-channel and p-channel. They can also be classified as Depletion MOSFETs and Enhancement MOSFETs.

Figure 1: 600 Volt SJ-MOSFET structure and circuit symbol.

What is an IGBT?

IGBT stands for Insulated Gate Bipolar Transistor.

Figure 2: 600 Volt G6H Trench IGBT structure and circuit symbol.

While the structures of MOSFETs and IGBTs might appear similar at first glance, a crucial difference lies in the addition of a p-substrate beneath the n-substrate in the IGBT.

There are two primary IGBT structures:

• NPT-IGBT: Also known as a homogeneous structure.
• PT-IGBT: Also known as an epitaxial structure. PT-IGBTs exhibit characteristic epitaxial layers with an N+-doped region (buffer layer) and an N—region on a p-doped substrate wafer. NPT-IGBTs utilize a homogeneous N—doped wafer. A specially formed p-layer is created on the backside during wafer processing.

MOSFET vs IGBT: Choosing the Right Device

When deciding between an IGBT and a MOSFET, consider the breakdown voltage requirements. Generally:

• IGBTs are preferred for breakdown voltages greater than 1000V.
• MOSFETs are preferred for breakdown voltages less than 250V.

Figure 3: Comparison of output characteristics between MOSFET and IGBT.

Tabular Comparison: MOSFET vs IGBT

The following table summarizes the key differences between MOSFETs and IGBTs, aiding in device selection based on application and design needs.

This comparison should provide a clear understanding of the differences between MOSFETs and IGBTs, facilitating informed decision-making for your specific application.