What is a wide bandgap semiconductor material?

According to Wikipedia: Wide-bandgap semiconductors (WBG or WBGS) are semiconductor materials that permit devices to operate at much higher voltages, frequencies and temperatures than conventional semiconductor materials like silicon and gallium arsenide. They are the key component used to make green and blue LEDs and lasers, and are also used in certain radio frequency applications, notably military radars. Their inherent qualities make them suitable for a wide range of roles, and they are one of the leading contenders for next-generation devices for general semiconductor use. "Wide-bandgap" refers to higher-energy electronic band gaps, the difference in energy levels that creates the semiconductor action as electrons switch between the two levels. Silicon and other common non-wide-bandgap materials have a bandgap on the order of 1 to 1.5 electronvolt (eV). Wide-bandgap materials in contrast typically have bandgaps on the order of 2 to 4 eV.

Note that 4 eV is not the limit of bandgap energies, as diamond has a bandgap of 5.5 eV and the beta phase of gallium oxide (Ga2O3) has a bandgap of 4.85 eV. See the related FAQ "WHAT IS AN ULTRA-WIDE BANDGAP SEMICONDUCTOR MATERIAL?"