Introduction

We will be adding new articles related to “power devices” to Tech Web’s “Basic Knowledge”. Recently, discrete devices such as diodes and transistors for handling large power with small loss, known as “power devices” or “power semiconductors”, have gathered attention. The reason is that power devices with higher efficiency and higher performance are needed to address “energy savings” and “miniaturization”, which are issues throughout the world.

However, what specific definitions should we use to categorize these “power devices” that one hears so much about today? Certainly there are no clear categories, but for example there are diodes and MOSFETs for AC-DC conversion or power switching with high voltage and high power, and then there are power modules that are modularized for output stages of power supply.

Here we will break things down into “silicon (Si) power devices” that are based on the conventional silicon semiconductor devices, and “silicon carbide (SiC) power devices” that have low loss and excellent characteristics in high-temperature environments compared to Si devices, and which are therefore expected to be the next generation low-loss elements. SiC transistors have already come into practical use, and have even been used in automotive equipment that has strict requirements for quality and reliability. The term “SiC” may make you think of special applications that handle huge amounts of power, but in fact these are power devices that make a large contribution to energy saving and miniaturization in many familiar applications.

SiC Power Devices

We will break down our discussion of SiC power devices into the following four sections:

1. What is SiC?
   • Material properties and Comparison with Si
   • Development Background
   • Advantages of SiC
2. SiC-SBD (Schottky Barrier Diode)
   • Comparison with Si Diode
   • Application Examples
3. SiC-MOSFET
   • Comparison with Various Types of Power MOSFET
   • Application Examples
4. Full-SiC Module
   • Module Structure
   • Switching Loss
   • Practical Points for Application

SiC is a compound semiconductor that is extremely stable?thermally, chemically, and mechanically?so the parameters that are important for power devices are extremely good. As elements, they can have low resistance, high speed operation, and high-temperature operation surpassing Si semiconductor devices, and they can greatly reduce energy loss in various types of power conversion ranging from power transmission to end devices.

For power devices using SiC semiconductor, there was volume production and shipment of SiC-SBDs (Schottky barrier diodes) and SiC MOSFETs in 2010*1, and volume production of “full-SiC” power modules using SiC for MOSFETs and SBDs in 2012*1. There has already been volume production of second-generation devices, so their evolution is accelerating. (*1 : initial volume production by ROHM either in Japan or globally)

In the first section, written for engineers who have little familiarity with SiC, we will start with the basics such as the material properties and advantages of SiC. After that, for SiC-SBDs, and then for SiC-MOSFETs, we will compare them with Si devices in order to explain differences such as in their characteristics and usage, and we will also provide application examples.

Full-SiC modules are modules that are optimized as power stages and have various advantages. In addition to talking about their characteristics, we plan to explain specific, practical points for their actual applications.

SiC power devices are extremely useful for power saving and miniaturization, and we hope to cultivate your understanding and provide you a chance to use them as familiar devices.

• SiC power device
• SiC-SBD
• SiC-MOSFET
• Full SiC power module