Wide-bandgap semiconductor

Wide-bandgap semiconductors 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 intrinsic qualities make them suitable for a wide range of other applications, and they are one of the leading contenders for next-generation devices for general semiconductor use. The wider bandgap is particularly important for allowing devices that use them to operate at much higher temperatures, on the order of 300 °C. This makes them highly attractive for military applications, where they have seen a fair amount of use. The high temperature tolerance also means that these devices can be operated at much higher power levels under normal conditions. Additionally, most wide bandgap materials also have a much higher critical electrical field density, on the order of ten times that of conventional semiconductors. Combined, these properties allow them to operate at much higher voltages and currents, which makes them highly valuable in military, radio and energy conversion settings. The US Department of Energy believes they will be a foundational technology in new electrical grid and alternative energy devices, as well as the robust and efficient power components used in high energy vehicles from electric trains to plug-in electric vehicles. Most wide-bandgap materials also have high free-electron velocities, which allows them to work at higher switching speeds, which adds to their value in radio applications. A single WBG device can be used to make a complete radio system, eliminating the need for separate signal and radio frequency components, while operating at higher frequencies and power levels. Research and development of wide-bandgap materials lags behind that of conventional semiconductors, which have received massive investment since the 1970s. However, their clear inherent advantages in many applications, combined with some unique properties not found in conventional semiconductors, has led to increasing interest in their use in everyday electronic devices to replace silicon. Their ability of handle higher energy densities is particularly attractive for attempts to continue obeying Moore's law, as conventional technologies appear to be reaching a density plateau. Wide-bandgap materials have several characteristics that make them useful compared to narrower bandgap materials. The higher energy gap gives devices the ability to operate at higher temperatures, as bandgaps typically shrink with increasing temperature, which can be problematic when using conventional semiconductors. For some applications, wide-bandgap materials allow devices to switch larger voltages. The wide bandgap also brings the electronic transition energy into the range of the energy of visible light, and hence light-emitting devices such as light-emitting diodes (LEDs) and semiconductor lasers can be made that emit in the visible spectrum, or even produce ultraviolet radiation. Solid-state lighting using wide-bandgap semiconductors has the potential to reduce the amount of energy required to provide lighting compared with incandescent lights, which have a luminous efficacy of less than 20 lumens per watt. The efficacy of LEDs is on the order of 160 lumens per watt. Wide-bandgap semiconductors can also be used in RF signal processing. Silicon-based power transistors are reaching limits of operating frequency, breakdown voltage, and power density. Wide bandgap materials can be used in high-temperature and power switching applications. There are many III–V and II–VI compound semiconductors with high bandgaps. The only high bandgap materials in group IV are diamond and silicon carbide (SiC). Aluminum nitride (AlN) can be used to fabricate ultraviolet LEDs with wavelengths down to 200–250 nm.