In everyday life, we are profoundly dependent on non-renewable energy such as fossil fuels to run trains, buses, cars, airplanes, ships and many others. However, these fossil fuels are limited and are causing environmental pollution. Also, there is an increasing demand for energy due to the growing population. To meet these demands, different kinds of renewable energy are being explored like solar energy, wind energy, tidal energy, geothermal energy and many more. Among them, solar energy has a great potential, as the counterparts need turbines which are noisy and require maintenance. But the main limitation of renewable energy is cost and efficiency. As the availability of fossil fuels is limited, its prices have gone up and the prices for the solar power modules have decreased.
The photovoltaic energy mainly requires high power, low-loss, faster switching and reliable semiconductor devices to increase the efficiency, power density and reliability. Silicon Carbide (SiC) and Gallium Nitride (GaN) devices are providing a promising solution to photovoltaic energy requirement and also to meet the increasing demand of energy. These devices have attractive characteristics like fast switching speed, low switching loss, high voltage blocking capability and high operating temperatures.
Silicon carbide (SiC) is a wide bandgap material (3.26eV) and a compound of silicon and carbon of group IV elements. It has thrice the bandgap, thrice the thermal conductivity and ten times the critical electric field strength than that of silicon. Due to these properties, SiC is the material of choice for power semiconductor devices.
Also, SiC’s mechanical strength and inertness to exposure in corrosive environments has attracted much attention. There are two modification of SiC, cubic and hexagonal. SiC are synthesized by pyrolysis of organosilicon polymers, small carbosilane and organosilane molecules.
Some of the methods used are chemical vapor deposition (CVD), condensed phase methods and metal condensation of halogen-silanes. SiC are used in high-temperature application such as in engines, cutting tools, construction of reactors and turbine parts. It is also used in the generation of solar power, LEDs, SiC-MEMS devices and many others.
As silicon carbide has better properties than silicon, it is being used as power devices in power electronics technology. These SiC power devices are being utilized for solar power generation, to make it cost effective. The photovoltaic inverter which is one of the main components in solar energy conversion system, its performance depends on the design of the power electronics.
The main aim is to maximize the power from the solar panels by minimizing the power loss in the energy conversion system, by reducing the number of power electronic components and by proper selection of the semiconductor devices. These can be achieved by using SiC which is a high power and high-temperature semiconductor material.
SiC is not only used in solar power generation but it is also utilized in different market segments like IT and electronics, buildings, renewable and grid, transportation and many more. By 2020, the demand for the power electronics will be around $2.4billion. About 87% of the demand is for the consumer electronic devices like phones, tablets, etc.
Another property of SiC i.e., thermal conductivity which is high, can be utilized as a natural heat sink. It helps flow the heat away from the semiconductor junction. Also, the saturated drift velocity of electrons in SiC is twice than that of the silicon. It allows high frequency switching and larger device current. Thus SiC devices in a renewable energy system can help remove a number of issues which are present due to the material limitations of silicon. Also SiC power MOSFET can be used instead of silicon IGBTs in the development of power electronics for solar applications.
Even though SiC has better material properties, there are some limitations of the technology. The device manufacturing cost of SiC is much higher than the counterparts. It also requires high-temperature packaging techniques to utilize the high thermal properties of the SiC. One of the major drawbacks is SiC P-N junctions have a high built-in potential when compared to the silicon.
These factors limit the extensive use of SiC devices. Therefore research is still under process to develop a commercially viable high power semiconductor device. The future research will focus on the ways to reduce the manufacturing cost, packaging issues and to increase the performance and reliability of SiC devices.
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