This post discusses attributes of gallium nitride (#GaN) that make it a disruptive technology and identifies the four factors required for GaN technology to displace silicon as the technology of choice.
Displacing the Silicon with GaN
38 years ago, when I first entered the semiconductor business as a freshly minted Stanford Ph.D., my first project was to develop a transistor that would be better than the aging silicon-based bipolar transistor that was invented in 1947 at Bell Labs by Brattain, Bardeen, and Shockley (They won the 1956 Nobel Prize for this development). My colleague, Tom Herman, and I set out to disrupt this 30 year old technology by using the latest techniques developed for integrated circuits. From this effort, and an incredible team of contributors, came the power MOSFET (We branded ours the HEXFET). It was a disruptive technology, and it did largely displace the bipolar transistor over a period of about 15 years. The dynamics of this transition taught us that there were four key factors controlling the adoption rate of a new semiconductor technology:
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Let’s now address each of these questions individually for the next generation of technology – GaN compared with silicon in the field of power conversion.
Does it enable significant new applications?
Some examples of large new applications that are made possible primarily because of the higher switching speed of GaN transistors include:
- Envelope Tracking: This is a power supply technique that can double the energy efficiency of RF power amplifiers used to transmit all of our voice and data through satellites, base stations, and cell phones. Envelope tracking is accomplished by tracking the power demand precisely and providing the power to exactly fit the amplifiers signal modulation needs. Today, RF power amplifiers operate at a fixed power level delivering maximum power whether or not the transmitter needs it. Excitingly enough, GaN transistors are the first transistors capable of tracking power demands at the high data transmission rates used in 4G LTE network base stations!
- Wireless Power: Cut the cord! Wireless power transfer enables cell phone, game controllers, laptop computers, tablets, and even electric vehicles to re-charge without being plugged in. A high frequency standard (6.78 MHz) for power transmission is currently being adopted by an industry consortium(A4WP). Silicon power devices (power MOSFETs) do not perform well at speeds this fast, whereas GaN transistors and integrated circuits offer an alternative that switches fast enough to be ideal.
- LiDAR (Light Distancing And Ranging): LiDAR uses pulsed lasers to rapidly create a three dimensional image of a surrounding area. This technique is widely used for geographic mapping functions and is technology driving (so to speak) “driverless” cars. The higher switching speed of GaN transistors drive superior resolution and response time that enable LiDAR applications beyond the mapping functions to applications such as augmented reality and fully autonomous vehicles.
Is it easy to use?
At EPC we designed our GaN transistors (eGaN FETs) to be very similar in behavior to the aging power MOSFETs, and therefore power systems engineers can use their design experience with minimal additional training. To assist design engineers up the learning curve, EPC has established itself as the leader in educating the industry about gallium nitride devices and their applications. As a matter of fact, in addition to publishing over 100 articles and presentations, in 2011 EPC published the industry’s first GaN transistor textbook (in English and Chinese) – GaN Transistors for Efficient Power Conversion. The second edition was published in 2015 by J. Wiley and is available through Amazon as well as textbook retailers. EPC is working with more than 60 universities around the world in order to lay the groundwork for the next generation of highly skilled power system designers trained in getting the most out of GaN technology
Is it VERY cost effective?
GaN transistors and integrated circuits from EPC are produced using processes similar to silicon power MOSFETs, and actually have many fewer processing steps than MOSFETs. In addition, GaN transistors do not require the costly packaging needed to protect their silicon predecessors. This packaging advantage alone can cut the cost of manufacture in half and, combined with high manufacturing yields, has resulted in the cost of a GaN transistor from EPC to belower in cost than a comparable (but lower performance) silicon power MOSFET. Today the designer does not even need to take advantage of the higher performance of GaN to realize cost savings in the system!
Is it reliable?
To date, tens of millions of hours of stress testing from several manufacturers, and tens of billions of device hours in demanding applications such as truck headlamps, drones, and base stations suggest this technology is capable of performing at acceptable levels of reliability in commercial applications today.
Summary
Thus, fast switching speed, small size, competitive cost, and high reliability give the GaN transistor the attributes needed to displace the silicon MOSFET in power conversion applications. Similar analysis show that soon the same will be true for analog integrated circuits. Perhaps in 3-5 years the same will be true for digital integrated circuits. GaN is a relatively new technology and has just begun its journey up the learning curve!
Also read: GaN Technology for the Connected Car
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