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Semefab, a UK based semiconductor manufacturer, will enter mass production of silicon-carbide Schottky diodes using a patented technology developed at the Queensland Micro- and Nanotechnology Centre at Griffith University.

Sales of electric cars doubled in 2021 to a new record of 6.6 million, according to Global Electric Vehicle Outlook. Even with the current strains in our global supply chains, electrical vehicle sales continue to skyrocket. Securing this future growth will demand investment into diversifying battery manufacturing and parts innovation.

There are over 15,000 components in an electric vehicle. To provide stable supplies of some of the critical parts, the semiconductor supply chain requires collaboration across thousands of suppliers and thousands of global kilometres and includes research and development (R&D), production, and distribution.

Griffith University's SiC Schottky diodes in various stages of manufacture. Each aluminium square on the SiC wafer is an individual diode.

R&D underpins the supply chain as the source of innovation and technological advances in semiconductor component design, fabrication and testing.

Among those thousands of components is the diode, a semiconductor-based device that allows current to flow in only one direction through the material and acts as a one-way switch for current. Diodes are the most used semiconductor device in electronic circuits.

Common p-n junction diodes are based on an interface between two types of silicon (Si): p-type Si is connected to the positive terminal to form the anode (+ end), and n-type Si is connected to the negative terminal (– end), forming the cathode. Conventional current flows through the diode from the positive end to the negative end.

A Schottky diode is a different category of diode that consists of a junction between a metal and a n-type semiconductor, such as Si. The metal side acts as the anode, and the semiconductor acts as the cathode, meaning current can flow from the metal side to the semiconductor side, but not in the opposite direction. Schottky diodes exhibit faster switching between on/off states, which enables them to waste much less power compared to p-n junction diodes.

While Si-based Schottky diodes can offer significant advantages over their p-n junction counter parts, they cannot block current flow at high voltages. The ability for diodes to operate at high voltages is crucial for applications such as solar power inverters, electric motor drives, electric vehicle (EV) chargers, and uninterruptable power supplies.

This technical roadblock has been removed by changing the semiconductor material from Si to silicon carbide (SiC) – a semiconductor that can withstand ten times higher electric field (voltage) and has three times higher thermal conductivity (heat removal capability) than Si.

But every R&D innovation in a component comes with unwanted complications. Fabrication and production equipment is optimised for the existing technology. A switch to a new technology often requires expensive retooling of existing fabrication equipment or the introduction of a completely new process. With a smaller number of companies equipped for fabrication of the new device, the result is a destabilisation of the supply chain.

Researchers at Griffith University and ANFF-QLD have developed and patented new SiC Schottky diode technology that features improved diode performance and can be manufactured by standard silicon-processing equipment. Because their SiC process re-design does not require retrofitting or new fabrication machines, their revolutionary technology reduces the fabrication cost and eliminates costly capital investment required by the existing design of SiC devices.

Attracted by the growing demand for more efficient and smaller energy-conversion systems, Semefab and Queensland Semiconductor Technologies Pty Ltd (Semefab’s subsidiary) have partnered with Griffith University to transfer the SiC technology to Semefab’s newly open fabrication line for power semiconductors. Starting this year, Semefab is expanding their power product offerings for commercial product manufacturing, and the first product offered will be the SiC Schottky diode produced with Griffith University’s patented method.