Featured Article: Next Generation Power Semiconductor: What is GaN / SiC ? Sanken and Next Generation Semiconductors

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Part 1. Next Generation Power Semiconductors: What is GaN / SiC?

GaN / SiC with Superior Characteristics

- History of Semiconductors - From Germanium to Silicon

History of semiconductors began around 1950 with the introduction of the point contact transistor. Initially, germanium was used, however silicon has become the primary material in semiconductor products due to its superior characteristic, and is still being used today.
Silicon semiconductor products have evolved over time, with the creation of high precision semiconductor manufacturing equipment and the optimization of device configuration and wafer process. This contributed to the development of a compact and high-performance electronic products which have become a major part in our daily lives.
However, the ability to improve the performance of silicon based semiconductors significantly becomes close to limitation within their own material properties.

Transition of semiconductor materials

-The Future- Next Generation Power Semiconductors "SiC" "GaN" 

SiC (silicon carbide) and GaN (gallium nitride) are receiving much attention as the next-generation materials to replace silicon.
Silicon is a simple substance. Whereas, SiC is a compound of carbon and silicon, and GaN is a compound of gallium and nitrogen. Therefore, semiconductors using these compounds are called "compound semiconductors".
Compared to silicon, GaN and SiC have a wider band gap (Si: 1.1 eV, SiC: 3.3 eV, GaN: 3.4 eV), so they are also called "Wide Band Gap Semiconductors".
Wide-bandgap semiconductors are characterized by the dielectric breakdown field strength. This allows the withstand voltage layer to be made significantly thinner than that of silicon, when attempting to achieve the same breakdown voltage.

GaN, SiC power semiconductors with various names

Excellent Physical Properties of SiC and GaN

Comparing the material itself of the wide band semiconductors, the figure of merit (εμeEc3) of SiC is 440 times greater, and GaN is 1130 times greater, than that of silicon.
To fully utilize this material, developments in peripheral technologies are currently underway. A more compact and highly efficient electronic equipment can be created, by replacing conventional silicon semiconductors with a GaN or SiC based compound semiconductor.

In recent years, improvements in the quality of SiC wafer substrates used in semiconductor materials has led to the use of wafers with larger diameter. Accordingly, high current and low cost devices have been introduced, and are beginning to be adopted in many equipment.

On the other hand, a GaN wafer substrate is still expensive, and a horizontal structure with a GaN active layer formed on a low cost silicon substrate is generally adopted. Therefore, although it is difficult to create a high current product, by shrinking the process, GaN is expected to be used in applications that require extremely high-speed switching operation.

Characteristics of silicon, SiC, GaN elements

Application of SiC / GaN Devices to Replace Silicon Devices

Differentiation of silicon, SiC, GaN

SiC Device Has an Advantage in Motor Drives and Other High Voltage / High Current Applications

SiC is a compound which replaces half of silicon with carbon. Carbon and silicon are tightly bonded, and the crystal structure is more stable than a single crystal silicon. Therefore, SiC has high dielectric breakdown field strength and can make the active layer very thin. This enables a device with higher breakdown voltage and lower loss than the conventional silicon devices.
SiC devices are becoming increasingly popular in the areas of high current and high withstand voltage, as a replacement for silicon IGBTs.
Specifically, they are expected to expand in the area of 10 kW or more, where there are great advantages in creating compact and light weight systems. This includes applications such as power conditioners for power generation systems, HEMS for electric homes, and electric vehicles (EV).

GaN Device Has an Advantage in Switching Power Supplies and Other Compact / High Frequency Applications

GaN has an even more stable bond structure, and higher dielectric breakdown field strength than SiC.
Currently, a GaN active layer formed on a silicon substrate is the general structure of a GaN device. Therefore, although it cannot have a higher breakdown voltage than SiC devices, it is suitable for high frequency applications. In the case of a switching power supply, it is possible to downsize inductors and other peripheral components, by switching at a high frequency.
GaN devices are expected to be applied in power supplies of 1 kW or less, in fields where there are high demand for compact designs.
For example, GaN devices are expected to be used as a power source for base stations in the 5th generation mobile communication systems (5G) , a market that is expected to expand in the years to come.
In addition, with the establishment of the USB Power Delivery (USB-PD) standard, power capacity up to 100 W can be received and supplied through a USB cable, and thus chargers for smartphones, laptop computers are becoming standardized. Conventionally, compact smartphone chargers have been preferred, and there is demand for fast charging product that are compatible with laptops and other medium-sized electronic devices, without changing the size. GaN devices are the most suitable for achieving this, and the spread of GaN devices are expected to accelerate in the future.

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Next PagePart 2. Applications Where SiC and GaN Devices are Expected to be Used
  In the following page, we will introduce nine applications where next-generation power semiconductors are expected to be adopted.

Part 1. Next Generation Power Semiconductors: What is GaN / SiC?
   ■ Characteristic of SiC / GaN Devices
   ■ Application of SiC / GaN Devices to Replace Silicon Devices

Part 2. Application of SiC / GaN Devices
   ■ 9 Applications Where SiC and GaN Devices are Expected to be Used

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