GaN Transistors for a Dollar? GaN Overcomes One Major Setback
The price of gallium nitride (GaN) transistors has dropped to less than $1.00 USD, becoming a cost-effective option for manufacturers. Could this lower cost finally push silicon from its throne?
The search for the next top semiconductor is always a priority. At this point in time, it seems like gallium nitride (GaN) could have the most potential in taking down silicon (Si); however, one of the challenges this material faces is how much it costs.
In 2012, a 2" GaN substrate price was around $1,900 while a 6" silicon substrate would be under $50 a unit. At the start of 2020, manufacturers have begun coming forward with cost-effective GaN-based technology that challenges silicon.
Power vs frequency for the top three wide-bandgap semiconductor materials. Image used courtesy of Kemet
Imagine a GaN device costing less than a silicon-based device. This cost-effectiveness could make a compelling case that GaN can be chosen over silicon when wanting less power losses, higher power density, smaller footprint, and lower costs.
Hoping to make this a future reality, GaN Systems, a leading GaN-based manufacturer, has designed a low current, high volume GaN power transistor for consumer and industrial applications while costing less than $1.00.
For the last 14 years, Efficient Power Conversion (EPC) has advocated for GaN technology claiming that GaN would one day crush silicon in semiconductor development; however, there are good reasons for EPC's claim. GaN transistors and integrated circuits (ICs) are processed similarly to silicon, thus preventing the manufacturing process from being altered too drastically.
The other reason being that the GaN-based substrate will be smaller in size for low voltage applications (<500V), which will cut the packaging costs 50% than silicon-based packaging.
Few developers have created GaN-based solutions that outperform silicon while costing less to manufacture, which makes EPC's solution of interest. Let's take a look at a solution from EPC that leverages GaN to make a more efficient component.
EPC’s 400W GaN Solution
Early this year, EPC announced a new 400W motor drive with an integrated GaN power stage. With the full PCB size of 81 mm x 75 mm, it would not be possible for silicon to be used for this PCB footprint. Silicon is larger than GaN substrates which gives EPC's board the advantage.
The EPC2152 80V, 15A ePower Stage board, provides independent control inputs and acts as the gate driver for the power board. The entire 400W power board, the EPC9146, holds three half-bridge circuits and the EPC2152.
Block diagram for EPC2152. Image used courtesy of EPC
For high voltage lateral GaN transistors, all electrical connections are located on the same side of the die, allowing for the elimination of complex, performance-limiting, two-sided packaging common in vertical Si power MOSFETs.
Chip-scale packaging is a more efficient form of packaging that reduces the resistance, inductance, size, thermal impedance, and cost of power transistors, enabling unmatched in-circuit performance.
The benefits of creating more efficient and smaller designs are one major reason GaN will continue to scale and develop; becoming more cost-effective is just one more attribute to push GaN to the next level. Now that one solution using GaN has created a more efficient component, let's dive into GaN System's GaN portfolio to see what devices are using GaN.
GaN Systems’ Extensive GaN Portfolio
GaN Systems recently announced the addition of two new enhancement mode transistors to its broad GaN-based portfolio. The GS-065-011-2-L operates at 650V and can be utilized in 45W to 150W applications, ideal for consumer products such as chargers and laptop adapters. The GS-065-030-2-L also operates at 650V but can deliver up to 3,000W of power, making an option for larger systems such as data centers, industrial motor drives, 5G, telecom, and energy storage of which have been a major industry focus.
GaN System’s transistors feature lower on-resistance and increased thermal performance compared to silicon or silicon carbide. Image used courtesy of GaN Systems
CEO of GaN Systems, Jim Witham commented that it's no surprise that GaN is starting to be used in more products and designs since GaN has been able to deliver lighter, smaller, cooler, and now cheaper power system solutions in just a few years.
Electrical designers will have more confidence in choosing GaN power transistors over silicon because of the design flexibility GaN offers. These GaN transistors are fully equipped with thermal management capabilities and low on-resistance, which delivers low power losses at high power ratings.
Despite the enthusiasm, interest, and benefits, does GaN stand a chance against Si, or even silicon carbide (SiC) in the long run?
Will GaN Take Over?
Imec, a leading research facility in Belgium, develops new methods for nanoelectronics and digital technologies. In particular, how to generate GaN buffer layers for high-voltage applications.
For this recent breakthrough, Imec collaborated with AIXTRON, a deposition equipment provider for compound semiconductor materials. Imec and AIXTRON showcased a 200 mm GaN Epitaxy for 1200V applications that allow this device to go head-to-head with silicon-carbide (SiC)-based technology.
Silicon carbide is often chosen for high voltage applications because of its ability to operate at high temperatures and frequencies while providing high electron mobility. Both SiC and GaN are wide-bandgap semiconductors, but GaN holds an advantage over SiC by providing higher electron mobility, a smaller footprint, and higher thermal management.
The cost of utilizing SiC substrates is higher than GaN, and up until this point in time, GaN has been used up to 650V operating voltage. At 1200V, this GaN device, the AIXTRON G5+C, could be used for EVs and renewable energy systems. Designers at Imec and AIXTRON added a GaN epitaxial growth, which yielded a hard breakdown of 1800V.
Adding fuel to the fire, back in February, Infineon published an article on cost savings for GaN-based power supplies in comparison to silicon. Below are some results that show circuits powered by GaN technology will return higher efficiency than silicon and higher power density at the same efficiency levels.
Comparing silicon and GaN to see the power density and efficiency ratio over time. Image used courtesy of Infineon Technologies
As time moves forward, research corporations such as Imec will not be the only ones aiming to replace high-voltage SiC instances with GaN technology. Many reasons make a case for GaN, especially as the original setbacks of cost per unit and added fabrication process costs were the main concerns for not fully committing to GaN technology over silicon. With GaN power transistors prices going under $1, it could be only a matter of time before GaN takes command of the semiconductor industry as the go-to material.