Table of Contents
Silicon has been historically applied as the dominant and favorite electric conduction material for power transistors, due to its many advantages that are absent with the other electric conduction materials, such as ease of controllability, high efficiency, low cost and high electric conduction reliability. However, the search of more effective electric conduction materials for power transistors has led to the discovery of gallium nitride (GaN), which has proven to be superior to silicon in various different ways. The outcome is the development of power transistors that use GAN grown on silicon, to ensure taking advantage of all the electric conduction advantages offered by both silicon and GAN materials, to replace the traditional silicon-based power MOSFETs.
Electric conduction has experienced history of competing interests between the silicon and the GAN devices. The major factor determining which material is preferable over the other in power transistor designing includes efficiency, reliability, cost-effectiveness and controllability (Lidow & Strydom, 2012). While one of the materials between silicon and GAN may have more than one of these electric conduction characteristics, it is important to distinguish which material offers the greatest advantage over the other. Therefore, this discussion seeks to summarize two major studies on the silicon-based MOSFETs and GaN-on-silicon FETs, with a view to demystify their differences in regards to electric conduction and preference for use in power transistor designs.
Summary: Main Paper
The concept of power transistor design technologies has a long history. Power MOSFETs are particularly common components of the history of electric power conduction and use, with a history dating back to over four decades ago. The improvements that have occurred to enhance the efficiency of power MOSFETs over the years are many. In the late 1950s, silicon power MOSFETs were the most common, obviously due to the numerous advantageous electrical characteristics of silicon, which are not available to many electrical materials. Silicon was adopted as the electrical conduction material since the 1950s due to its ease of use, flexibility to new usage, high reliability and lower costs (Lidow & Strydom, 2012). Nevertheless, starting the 2000s, the unusually high electron mobility characteristic of gallium nitride (GaN) was discovered, resulting in the use of gallium nitride grown on silicon carbide that produced higher power gains (Lidow & Strydom, 2012). Consequently, the use of silicon as the dominant electrical conduction material was interrupted by the introduction GAN, although it never replaced silicon fully as an electric conduction material for power transistors.
The suitability and economic viability of electrical semiconductors is informed by four major factors namely the material’s controllability, efficiency, reliability and cost-effectiveness (Lidow & Strydom, 2012). Among these, GAN offers two major advantages of silicon when it comes to application as electrical conduction materials. First, GAN has higher critical electrical fields, which allows for the use of a smaller GAN for a certain electrical voltage, compared to the required silicon size. The other notable advantage offered by GAN over silicon as an electrical conduction material is GAN’s lateral structure, which allows for its flip-chip packaging, thus producing a superior electrical conduction power device that has a higher performance packaging, which is significantly smaller than any other available electrical conduction material’s devices (Lidow & Strydom, 2012). The major disadvantage associated with GAN over silicon as electric conduction materials, is that GAN electric conduction devices are relatively more expensive to produce than silicon devices. Nevertheless, the major advantage that came with the introduction of GAN as an electric conduction material over the use of silicon is that, GAN has resulted in a significant reduction in the levels of difficulties involved in developing power conversion systems, due to the very high voltage switching capabilities of GAN (Lidow & Strydom, 2012).
Summary: Chosen Paper
The more advanced GAN grown on silicon power transistors, simply referred to as GaN-on-silicon FETs, can broadly displace the traditional power MOSFETs. However, the major challenge is getting a customer to accept the new technology, since all the customer wants is the same old technology at a reduced cost (Extance, 2013). Therefore, for the new technology to penetrate in the market, all the GaN-on-silicon FETs manufacturing companies need to do is to enhance the reliability of these devices and ensure to offer them at competitive costs.
Silicon-based power MOSFETs and the GaN-on-silicon FETs are two very highly competing power transistor devices, with each device offering a notable advantage over the other one. The key difficulty associated with choosing the GaN-on-silicon FETs over the silicon power MOSFETs is that both perform at an almost equal electric conduction level of efficiency.
The major difference between the silicon MOSFETs and the GaN-on-silicon FETs is that in the silicon devices, power flows vertically, while in the GAN devices, power flows horizontally , giving the GAN devices an upper hand over the silicon devices, due to their higher electric current switching speed (Extance, 2013). Therefore, the GAN devices are better for power transistor devices with 600 V and below, while the silicon-based power MOSFETs are the most suitable for higher voltage devices with 600V and above (Extance, 2013). The GaN-on-silicon FETs and the silicon-based power MOSFETs really compete at the 600V, making it very difficult to prefer one over the other at this voltage range.
Nevertheless, at the 600V, the GAN devices are much smaller compared to the silicon devices, which then give the GAN devices an upper hand. However, at high temperatures of above 800V, the GAN devices do not really hold, making the high voltage ranges a dominant territory for the silicon devices. Notwithstanding these significant differences, there has been a protracted effort to make the GAN devices for tolerant to high voltages, with indications that it is now possible to have GAN devices that operate effectively even at voltages as high a 1700V (Extance, 2013).
The history of electric conduction power transistors has seen the silicon-based MOSFETs continue to compete at almost equal levels with the GAN devices. The silicon MOSFETS were the historically dominant power transistor devices starting the late 1950s through to the 2000s, when the electric conduction advantages of gallium nitride was discovered, resulting in the production of the GAN grown on silicon power transistors. These devices combines the advantages offered by both silicon and GAN as electric conduction materials, to produce a more superior electric conduction device compared to the traditional silicon MOSFETs. Nevertheless, while the GAN devices are superior at low voltage levels below 600V, the silicon devices are the most reliable and efficient at higher voltage levels above 600V. Consequently, the major difficulty in selecting one device over the other is that the silicon and the GAn devices perform at equally competitive levels in electric conduction at 600V.
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- Extance, A. (2013). SiC and GaN power devices jostle to grow their role. Industry Review 9, 6-9.
- Lidow, A. & Strydom, J. (2012). Gallium Nitride (GaN) Technology Overview. Efficient Power Conversion Corporation, 1-6.