Industry-First 1200 V GaN-on-Sapphire MOSFET

Transphorm has announced the availability of the Verilog-A model and datasheet specifications for its new 1200 V GaN-on-Sapphire MOSFET. According to the company, this is the first-ever 1200 V GaN-on-Sapphire transistor to be demonstrated in the power semiconductor market.    

1200 V GaN-on-Sapphire MOSFET. Image used courtesy of Transphorm

 

Compared to traditional silicon, constructing GaN devices on sapphire allows for a much higher operating voltage due to sapphire’s better insulating properties, critical for emerging EV and three-phase power applications. 

Engineers use a Verilog-A model to simulate circuit components, like MOSFETs, in their virtual designs to reduce hardware design times and iterations.

 

GaN-on-Sapphire Extends Operating Voltage

According to a recent technical paper published by Transphorm (1200 V GaN Switches on Sapphire Substrate), the new 1200 V GaN switches are made with HEMTs (high electron mobility transistors) on sapphire as opposed to traditional silicon substrates. The better insulation of sapphire allows for fast-switching, low-loss devices to operate at much higher voltages than traditional GaN-on-Silicon.

GaN transistors constructed on silicon typically support voltages up to 650 V, so 1200 V represents a significant step forward in the technology. 

 

 150-mm GaN-on-sapphire wafer with 1200 V switches. Image used courtesy of Transphorm

 

Transphorm’s GaN-on-Sapphire process is already in high-volume production for products in the LED market, which according to the company, has allowed the process to mature and maintain a high level of reliability.  

 

SuperGaN Technology

In addition to sapphire substrates, the new 1200 V devices are based on Transphorm’s SuperGaN technology. SuperGaN uses a normally-off low-voltage silicon MOSFET and a normally-on high-voltage GaN HEMT device to operate as a single switch. This construction allows the GaN switches to run faster and with greater efficiency. 

 

Transphorm GaN switch configuration. Image used courtesy of Transphorm

 

EV Battery Voltages Increase

To achieve higher power densities and better vehicle performance, EV battery bus voltages are increasing from 400 V today to 800 V and beyond by the end of this decade. The higher bus voltages demand power conversion components with higher voltage ratings up to 1200 V. WBG (wide bandgap) technologies like GaN (Gallium Nitride) and SiC (Silicon Carbide) are competing head to head within the fast-growing EV market to capture BOM share in high voltage and power dense powertrain and battery systems like traction inverters, on-board chargers (OBC) and DC-DC converters.   

 

Hyundai IONIQ 5 EV with 800 V battery. Image used courtesy of Hyundai

 

Each WBG technology brings its own unique set of features and capabilities, but higher voltage applications (1200 V or higher) have trended toward silicon carbide, with most GaN FETs limited to only 650 V.

With the introduction of their GaN-on-Sapphire device, Transphorm believes it can shift this dynamic by offering a 1200 V GaN device that meets the voltage requirements of 800 V powertrains, as well as high voltage three-phase industrial and energy power systems.

Along with the 1200 V withstand voltage, the company claims their new solution offers system designers higher power density with equal or better performance with more competitive pricing than existing 1200 V solutions.      

To help back up this claim, the new device was validated in a 5 kW, 900 V to 450 V buck converter configuration where 98.76% efficiency was achieved at a 100 kHz switching speed, a notch higher than comparable SiC devices. The results of the testing are published in the company’s technical paper.

 

950 V to 450 V buck converter using 1200 V GaN switches. Image used courtesy of Transphorm

 

Buck converter efficiency with 1200 V GaN switches. Image used courtesy of Transphorm

 

Key Specifications

Along with a maximum load current of 29 A, some key specifications for the new MOSFET  include:

• 70 mΩ RDS(on)
• Efficient bidirectional current flow
• ± 20 Vmax gate robustness
• Low 4Vth gate drive noise immunity
• Zero QRR
• 3-lead TO-247 package

The first physical samples of the new device should be available by Q1 2024.