Scientists in Japan have built a transistor that can operate at 1,110 degrees Fahrenheit, a breakthrough that could allow future spacecraft to survive on the surface of Venus far longer than any probe has managed before.
According to Live Science, the device is a junction field-effect transistor, or JFET, made from silicon carbide. The researchers published details of how it works in a study on Aug. 17 in the journal APL Electronic Devices.
Venus presents one of the most hostile environments in the solar system for electronics. The planet's thick carbon dioxide atmosphere pushes surface temperatures to around 860 degrees Fahrenheit. The Soviet-era Venera 13 lander still holds the record for the longest a spacecraft has survived on the Venusian surface: 2 hours and 7 minutes. As the researchers noted in the study, "Past landers have been limited to only a few hours by silicon-based electronics."
Most consumer electronics, including smartphones and computers, rely on metal-oxide-semiconductor field-effect transistors, known as MOSFETs. These are easier to miniaturize but break down at extreme temperatures. JFETs can offer lower noise levels because they do not rely on an oxide layer, which can introduce interference, but they have historically been harder to scale down for practical use.
Silicon carbide has been viewed as a promising material for high-temperature electronics since at least the early 2000s. As the researchers put it, "Integrated circuits fabricated with SiC are particularly attractive for extreme environments, such as deep-space exploration, geothermal drilling, and aerospace engine control, where conventional silicon-based ICs cannot operate reliably."
The problem is that recently developed SiC-JFETs have consistently run into two issues: low controllability and large leakage currents. Both problems get worse at high temperatures. In a silicon carbide crystal, dopant atoms used to alter the material's electrical properties can penetrate deeper than expected into the substrate. Under normal conditions this causes no problems, but at high temperatures it throws off the voltage needed to open the transistor's channel, making it unreliable. The researchers found this effect can knock conventional JFET voltage thresholds off by more than 2 volts. Above 660 degrees Fahrenheit, the SiC substrate itself can also start to conduct electricity in ways that cause unwanted current leakage.
The new Japanese design addresses both of these problems, though the study does not detail how beyond describing changes to how the gate and channel regions are defined within the material. The device was tested up to 600 degrees Celsius, or 1,110 degrees Fahrenheit, well above the surface temperature of Venus.
No Venus mission currently uses this technology, but the research points toward a future where surface probes could operate for days or weeks rather than hours.
