The Rise of Wide-Bandgap Semiconductors
Wide-bandgap semiconductors and materials have been getting a lot of coverage lately. The primary reason is that, due to improvements in manufacturing wide-bandgap substrates, it is now possible to manufacture wide-bandgap semiconductors on 6- and 8-inch substrates, which, notably, brings down the cost to manufacture devices at volume. Considerable effort is also being made to develop technology that will eventually enable 300mm substrates that are free of defects. This will allow for high yields of wide-bandgap semiconductors, making them even more cost competitive.
What is a wide-bandgap semiconductor? Or better yet, what is a bandgap?
In all materials, there is a valence band and a conduction band. The band gap is how much energy it takes to get an electron to move from the valence band to the conduction band. Think of climbing the stairs – the energy it takes you to get to the next story is your bandgap. For conductive metals like copper or aluminum, the bandgap is very small; for semiconductor materials like silicon, it is slightly wider, between 0.6eV and 1.5eV. For wide-bandgap materials, which are between semiconductors and insulators, the bandgap is wider, with a value ranging between 2eV and 4eV.
Figure 1. Band gap. (2023, October 17). In Wikipedia.
Okay, so why does a wide bandgap matter?
Silicon carbide (SiC) and gallium nitride (GaN) are the two most common wide-bandgap semiconductors used today. The advantages of SiC and GaN semiconductors is their ability to operate at higher temperatures than silicon can, in part due to their higher thermal conductivity and faster switching capability. They have a higher breakdown voltage, and thus can operate at a higher voltage; in addition, the electrons move faster, which enables the chip to turn on and off faster, operating at a higher frequency. These favorable characteristics allow system designers to create switching systems that are smaller, are more efficient, and produce less heat than silicon chips.
This makes wide-bandgap semiconductors ideal for use in power semiconductors, field-effect transistors (FETs), and diodes, as well as in the communications space for use as RF devices. GaN is also the primary material in the LED space due to its optical characteristics of producing blue light. According to Yole Intelligence, automotive applications account for more than 70% of SiC power semiconductors. Energy, transportation, industrial, consumer, telecom and infrastructure, and other sectors fill out the remainder of the applications.
Benefits of wide-bandgap semiconductors
SiC power chips are key to the electric-vehicle (EV) automotive experience because SiC-based charging and battery systems enable faster charging times – approaching the same length of time needed to fill a conventional car with gas! Wide-bandgap semiconductors also enable higher energy efficiencies, providing a longer range for EV batteries and potentially allowing the batteries to be lighter and/or provide longer distances between charges. And all of this goodness comes at a lower system cost. In the electric grid, SiC and GaN power semiconductors will reduce power loss during switching, improving grid efficiency, which is becoming more important as the grid switches to renewables.
The lower cost, improved efficiency, smaller form factor, and reduced heat discharge are also attractive benefits for power supplies used in servers and industrial equipment. An added benefit is that fewer motor drive inverters are needed for industrial systems, which reduces cabling costs and system complexity.
Wide-bandgap semiconductors are also used in telecommunications applications. GaN is used in military radar applications as well as 5G base stations. The electrical characteristics of GaN, which include high frequency, high bandwidth, high power, and high efficiency, make it an ideal material for RF devices in the telecom industry. GaN allows for smaller systems, which use less power, operate cooler, and simplify the system. An added benefit is GaN’s power semiconductor properties, which the communications industry uses for power supplies for base stations as well as for charging mobile devices. This enables faster charging times, more efficient systems, and a smaller charging footprint.
Wide-bandgap semiconductors drive sustainability
The recent improvements in wide-bandgap substrate development and the underlying process technology have increased the availability of wide-bandgap semiconductors and helped to reduce their cost. The increasing number of companies manufacturing wide-bandgap semiconductors will continue to bring the cost down, allowing these devices to proliferate and support the growth of advanced electrification and communication systems. Ultimately, their improvements in costs, battery charging, and EV performance will entice consumers to make the transition to EVs sooner rather than later, which is good for the planet and everyone on it.
