Kyoto University researcher Created Field effect transistors based on silicon carbide (SiC) capable of operating at temperatures of 600 °C (873 K). The main feature of this development was the promise of mass production in modern factories. High-temperature transistors for space and propulsion applications are nothing new, but until now they required unique processes that severely limited their applications.
Image source: Kyoto University
This transistor is a JFET (junction field effect transistor) – a field effect transistor with a controlled pn junction. This high-temperature solution is the first to be manufactured using selective ion implantation, a doping technology widely used in conventional semiconductor production.
While conventional silicon is known to stop working at temperatures above about 250°C, the new SiC transistors are designed for operating conditions such as those inside aircraft engines and on the surface of Venus, which reach temperatures of about 460°C. At the same time, this unusual transistor and the circuits based on it can be produced in existing production facilities without the need for deep modernization.
A major problem with previous developments in this field was the instability of the threshold voltage during ion implantation manufacturing. When dopant ions are introduced into the crystal, they partially diffuse through the channels of the lattice, forming so-called “channel tails” that penetrate deep into the sides of the channels and contaminate the crystal. In the new transistor architecture, the researchers placed the gate beneath the channel. This arrangement makes it possible to compensate for the effects of negative effects of dopant ion scattering and to set the threshold voltage more accurately. In particular, at 400 °C, the difference between calculated and measured threshold voltages is less than 0.1 V and typically exceeds 2 V, and predictable operation of electronic devices cannot be based on such differences.
The second problem with SiC transistors is related to leakage current, which increases dramatically when heated. Additional electrical insulation is required between the transistor and the substrate, which reduces the leakage current by an order of magnitude at an operating temperature of 200 °C. However, the authors of the working note regret that further reduction of leakage current is not possible due to the fundamental properties of the silicon carbide material.
Image source: AI Generation Grok/3DNews
At the same time, the presented work demonstrates the feasibility of novel transistor architectures that can be used in high-temperature integrated circuits. The architecture is not yet fully developed; for example, researchers are not yet ready to create mature complementary pairs of such transistors, which are necessary to design complete and efficient logic. Like many others, from lithography to packaging, this work remains at the cutting edge. But just the promise of producing unique, high-temperature wafers in ordinary factories is valuable. Venus is waiting!
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