What Are Wide Band Gap Semiconductors?

Wide band gap semiconductors are a class of crystalline semiconductor materials whose energy band gap is substantially larger than that of silicon, which has a band gap of 1.1 electronvolts (eV). Commercially important wide band gap materials, including silicon carbide (SiC) with a band gap of approximately 3.3 eV and gallium nitride (GaN) at 3.4 eV, can sustain higher electric fields, operate at higher temperatures, and switch faster than silicon-based devices, making them central to advances in power electronics, radio frequency amplification, and high-temperature sensing. The field draws on solid-state physics, crystal growth engineering, device fabrication, and power electronics circuit design.

Interest in wide band gap semiconductors accelerated during the 1990s as epitaxial growth techniques for SiC and GaN matured sufficiently to produce low-defect wafers at commercially viable sizes. The physics underlying their performance advantages, including breakdown field strengths ten times that of silicon and higher thermal conductivity in SiC, have been analyzed in depth in publications including IEEE Transactions on Electron Devices and summarized by the IEEE Power Electronics Society in its coverage of wide-bandgap technology in industrial power conversion.

Material Properties and Device Physics

The wide band gap of SiC and GaN produces several correlated performance characteristics. A large band gap raises the intrinsic carrier concentration threshold, allowing operation at junction temperatures above 200 degrees Celsius without the leakage degradation that limits silicon devices. The high critical electric field, around 3 MV/cm for SiC and GaN compared to 0.3 MV/cm for silicon, allows drift regions in power transistors and diodes to be thinner and more heavily doped, dramatically reducing on-resistance for a given blocking voltage rating. GaN's high electron mobility of roughly 1500 cm²/Vs, combined with the two-dimensional electron gas (2DEG) formed at AlGaN/GaN heterojunctions, enables high-electron-mobility transistors (HEMTs) that operate efficiently at radio and microwave frequencies.

Silicon Carbide Devices

SiC devices are produced on wafers now available at four and six inch diameters, with continued progress toward eight inch wafer production that will reduce manufacturing costs. The primary SiC power devices in commercial production are the SiC metal-oxide-semiconductor field-effect transistor (MOSFET) and the SiC Schottky barrier diode. SiC MOSFETs replace silicon IGBTs in applications requiring switching frequencies above roughly 20 kHz or operating temperatures above 150 degrees Celsius. In electric vehicle traction inverters, SiC MOSFETs reduce switching losses sufficiently to allow smaller and lighter thermal management systems. Wolfspeed, STMicroelectronics, and other manufacturers supply SiC MOSFETs rated from 650 V to 1700 V for industrial and automotive use.

Gallium Nitride and Gallium Alloys

GaN-on-silicon and GaN-on-silicon carbide substrates are the dominant platforms for GaN power and RF devices. In power electronics, GaN enhancement-mode and depletion-mode HEMTs are used in converters operating at hundreds of kilohertz to several megahertz, a frequency range where silicon switches become inefficient. In RF applications, GaN HEMTs power base station amplifiers, radar transmitters, and satellite uplink systems, where their combination of high voltage operation and high frequency capability is difficult to match with other semiconductor platforms. The IEEE Spectrum analysis of gallium nitride and silicon carbide competition in power electronics documents market adoption across EV chargers, solar inverters, and 5G base stations. Gallium arsenide and gallium phosphide, other gallium alloys, serve complementary roles in optoelectronics and certain RF applications but have narrower band gaps than GaN.

Applications

Wide band gap semiconductors have applications in a range of fields, including:

• Electric vehicle traction inverters and onboard battery chargers
• Renewable energy inverters for solar and wind power systems
• 5G base station power amplifiers requiring high efficiency at microwave frequencies
• Industrial motor drives and switched-mode power supplies
• High-temperature sensors and electronics for aerospace and geothermal environments