Wide bandgap semiconductor materials
The energy of electrons in solids has discontinuous values, and electrons are distributed in some discontinuous energy bands. The gap between the band of valence electron and that of free electron is called band gap. So the width of the band gap actually reflects the extra energy that the bound valence electron must obtain to become a free electron. The bandgap of silicon is 1.12 electron volts (EV), and the wide bandgap semiconductors are those with bandgap width of 2.3 EV and above semiconductor material Typically silicon carbide (SIC), Gan, diamond and other materials. Wide band gap semiconductor materials are known as the third generation semiconductor materials.
- Chinese name
- Wide bandgap semiconductor materials
- Foreign name
- Wide bandgap semiconductor material
- Third generation semiconductor materials
- Evaluation standard
- Eg is greater than or equal to 2.3ev
- Diamond, SiC, Gan, etc
- Band gap width
- 3 EV and above
Wide bandgap semiconductor materials semiconductor material
With the development of microwave devices and optoelectronic devices, Ⅲ - Ⅴ family has been developed. However, the development of Electronics puts forward higher and higher requirements for devices, especially those that need high power, high frequency, high speed, high temperature and working in harsh environment. For example, the monitoring system of high-performance military aircraft and supersonic PA plane engine requires long-term operation at 300 ℃, while the general devices can only operate normally at 100 ℃: in terms of interstellar navigation, the surface temperature of mercury is 370 ℃ when it is close to the sun, while the surface temperature of Venus is higher, reaching 450 ℃, and the pressure is 10 ℃ seven However, the maximum operating temperature of silicon cell is only 200 ℃, although GaAs battery can work above 200 ℃, its efficiency is greatly reduced; higher frequency and higher power are required in communication field, all of which are unable to meet the requirements of existing Si devices or GaAs devices. In order to reduce the temperature of the device to 125 ℃ which can be tolerated by Si device, the cooling system must be equipped. If the device can work at 325 ℃, the volume of unmanned spacecraft can be reduced by 60% if the cooling system is removed. The demand of the times calls for the emergence of high temperature semiconductor materials. For those who study semiconductor materials, they are facing an exciting era because of the rapid progress in high-temperature semiconductors in recent years. 
Wide bandgap semiconductor materials Limitations of silicon materials
Silicon has been the main material used in power electronic devices. The reason for the high purity and low cost of monocrystalline silicon devices is that people have been researching on the high-purity and low-cost silicon devices for a long time. However, with the improvement of structure design and manufacturing process, the performance of silicon devices has approached the theoretical limit determined by material properties (although this limit has been broken again and again with the continuous innovation of device technology). Many people think that the potential of improving and improving the performance of power electronic devices and systems by relying on silicon devices is very limited. Therefore, more and more attention has been paid to power electronic devices based on wide bandgap semiconductor materials.
Wide bandgap semiconductor materials Wide bandgap of semiconductor materials
Due to the much wider bandgap than silicon, wide bandgap semiconductor materials generally have much higher critical avalanche breakdown electric field strength and carrier saturation drift velocity, higher thermal conductivity and carrier mobility, so power electronic devices based on wide band gap semiconductor materials (such as silicon carbide) will have much higher withstand voltage than silicon devices Low pass ability resistance It has better thermal conductivity and thermal stability, as well as stronger ability to withstand high temperature and radiation. However, the development of wide bandgap semiconductor devices has been restricted by the difficulties of material extraction, manufacturing and subsequent semiconductor manufacturing process. It was not until the 1990s that the refining and manufacturing technology of silicon carbide materials and the subsequent semiconductor manufacturing process made a breakthrough. At the beginning of the 21st century, silicon carbide based Schottky diodes were introduced, which had better performance than Silicon Schottky diodes. Therefore, they were rapidly applied in power electronic devices, and their overall benefits far exceeded the price differences between these devices and silicon devices The resulting cost increases. Gallium nitride Since the 20th century, there has been a breakthrough in the fabrication of other semiconductor materials based on substrate processing. Gallium nitride devices have attracted more attention due to their better high frequency characteristics than silicon carbide devices. Diamond has the best performance among these wide band gap semiconductors. Many people call it the most ideal or promising power semiconductor material. However, the extraction and manufacturing of diamond materials and the subsequent semiconductor manufacturing process are also the most difficult, and there is no effective way. There is still a long way to go before the emergence of power electronic devices based on diamond materials. 
Wide bandgap semiconductor materials application
Nitrided aluminum nitride (AIN) is also known as the most important type of nitride (AIN) - based semiconductor. Its main applications include:
(1) Lighting field: semiconductor lighting is a new type of high-efficiency, energy-saving and environmental protection light source. It will replace most of the traditional light sources used. It is called the revolution of lighting source in the 21st century. The development of GaN based high-efficiency and high brightness light-emitting diode (LED) is the core technology and foundation of realizing semiconductor lighting.
(2) Optical storage field: the optical storage density of DVD is inversely proportional to the square of the wavelength of semiconductor laser as a read-write device. The short wavelength GaN based semiconductor laser can increase the DVD optical storage density of the currently used GaAs based semiconductor laser by 4-5 times, which will become the mainstream technology of new optical storage and processing.
(3) Electronic devices: high temperature, high frequency and high power microwave devices are urgently needed in wireless communication, national defense and other fields. If the output power density of microwave power tube is increased by an order of magnitude, and the working temperature of microwave devices is raised to 300 ℃, a series of problems in aerospace electronic equipment and civil mobile communication system will be solved. Silicon carbide is another representative of wide band gap semiconductor materials. The working temperature of SiC can reach 600 ℃, and its excellent characteristics make it have broad application prospects in the development of high temperature, high frequency, high power, anti radiation devices, ultraviolet detectors, short wave light-emitting diodes and so on. 
- reference material
Cui Qingheng, Hua Xiaofeng . power conversion of photovoltaic power generation system China Water Conservancy and Hydropower Press ，2016.04
Jiang Minhua . amazing new materials Shandong science and Technology Press ，2013.10