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Transistors for Electric Motor Drives

ARPA-E Award: 
Goleta, CA
Project Term: 
09/01/2010 to 05/28/2013
Project Status: 
Technical Categories: 
Picture of Transphorm's transistor
Critical Need: 
All electric devices are built to operate with a certain type and amount of electrical energy, but this is often not the same type or amount of electrical energy that comes out of the outlet in your wall. Power converters modify electrical energy from the outlet to a usable current, voltage, and frequency for an electronic device. Power stations also use power converters on a larger scale to modify electrical energy so it can be efficiently transmitted. Today's power converters are inefficient because they are based on decades-old technologies and rely on expensive, bulky, and failure-prone components. Within the next 20 years, 80% of the electricity used in the U.S. will flow through these devices, so there is a critical need to improve their efficiency.
Project Innovation + Advantages: 
Transphorm is developing transistors with gallium nitride (GaN) semiconductors that could be used to make cost-effective, high-performance power converters for a variety of applications, including electric motor drives which transmit power to a motor. A transistor acts like a switch, controlling the electrical energy that flows around an electrical circuit. Most transistors today use low-cost silicon semiconductors to conduct electrical energy, but silicon transistors don't operate efficiently at high speeds and voltage levels. Transphorm is using GaN as a semiconductor material in its transistors because GaN performs better at higher voltages and frequencies, and it is more energy efficient than straight silicon. However, Transphorm is using inexpensive silicon as a base to help keep costs low. The company is also packaging its transistors with other electrical components that can operate quickly and efficiently at high power levels--increasing the overall efficiency of both the transistor and the entire motor drive.
Potential Impact: 
If successful, Transphorm's transistors would improve the energy efficiency of electric motor drives by 2-8%.
Efficient, variable speed motor drives could help reduce peak power demand, increasing the reliability of the power grid.
The energy savings from more efficient motor drives could power 13 million homes.
More efficient motor drives in the U.S. alone could save over $13 billion annually--money that could be spent to get the economy back on track.
Innovation Update: 
(As of May 2016)
With support from ARPA-E, Transphorm has developed commercially successful high-performance GaN high electron mobility transistor (HEMT) switches on low-cost silicon substrates. In February 2013, Transphorm announced that its 600V GaN module had enabled the world’s first GaN-based high-power solar converter, developed in conjunction with customer-partner Yaskawa Electric. The same year, Electronic Products Magazine named Transphorm’s 600V GaN HEMT the “Product of the Year” in the “Discrete Semiconductor” category. Multiple private investment groups have funded continuing development, including Google Ventures, Soros Quantum Strategic Partners, Fujitsu, and Kleiner Perkins Caufield and Byers. In 2015, investment firm KKR led a $70 million round of investment in Transphorm. After its ARPA-E project concluded, Transphorm continued to expand its portfolio of GaN transistor products, and as of early 2016 the company had more than 15 GaN/Si transistor products on the market. 
In order to demonstrate high voltage (600V and 900V) GaN-on-silicon normally-off power switches, the team had to overcome challenges of growing high-quality GaN layers on silicon substrates. Principally, the components’ mismatch of crystal lattice structure and coefficients of thermal expansion limit the functionality of a GaN/Si transistor. The team addressed this issue by developing unique buffer layer structures between the GaN and silicon. This innovation enabled the team to develop GaN switches that demonstrate faster switching speeds and lower gate charges over silicon MOSFETs, another type of transistor. 
For a detailed assessment of the Transphorm team's project and impact, please click here.
ARPA-E Program Director: 
Dr. Timothy Heidel
Project Contact: 
Dr. Primit Parikh
Release Date: