The material that changes everything: it works at temperatures that would destroy any other chip
A group of researchers from the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia has demonstrated for the first time that electronic devices based on beta-gallium oxide (β-Ga₂O₃) can operate reliably at temperatures close to absolute zero, specifically at 2 Kelvin (-271.1 °C), without exhibiting the freeze-out phenomenon that renders traditional semiconductors unusable in cryogenic conditions. The results were announced through an official university statement.
Why conventional chips fail at thermal extremes
The operation of semiconductors depends on the ability of electrons to cross an energy threshold - the bandgap - to reach the conduction band and generate current. At very low temperatures, electrons lose the thermal energy needed to make this jump and remain trapped, a phenomenon known as carrier freeze-out. "In practice, most conventional electronic devices start to fail when they drop below about 100 K (-173 °C)," explained Vishal Khandelwal, a former PhD student at KAUST.
At the other extreme of the thermal spectrum, as the temperature increases, electrons gain excess energy and are excited en masse into the conduction band even when the device should be in the 'off' state. The result is uncontrolled charge carrier increase, leading to electrical leakage, switching instability, overheating, and progressive degradation of the component.
Standard semiconductors like silicon, gallium nitride, and silicon carbide are subject to both of these failure mechanisms at thermal extremes. To address the issue, the KAUST team worked on beta-gallium oxide, an ultra-wide bandgap semiconductor (UWBG) that had previously been studied by the same group, which documented its resistance to ionizing radiation and high temperatures.
How beta-gallium oxide stays stable
The exceptional width of the bandgap of β-Ga₂O₃ makes it much more difficult for undesirable excitation of electrons into the conduction band, granting the material intrinsic resistance to leakage and thermal instability up to 500 °C - a threshold far exceeding that of silicon and any components present in current commercial devices, whose maximum operating temperature generally hovers around 150-200 °C.
To solve the freeze-out problem at cryogenic temperatures, the researchers employed heavy doping of β-Ga₂O₃ with silicon atoms. Doping involves the intentional introduction of impurity atoms within the crystal lattice of the host material to modify its electrical properties and make available free charge carriers. The high concentration of silicon atoms introduced into β-Ga₂O₃ creates an "impurity band" - a set of closely spaced energy states associated with the doping sites - through which electrons can migrate by hopping from one atom to another, without having to rely on thermal energy to reach the main conduction band.
This mechanism enables the material to maintain electrical conduction even under conditions where conventional semiconductors would completely freeze up. "At that temperature, there is almost no thermal energy to help electrons jump into the conduction band of gallium oxide. Instead, electrons hop through an 'impurity band' created by the silicon atoms, allowing the device to carry current," stated Xiaohang Li, Principal Investigator at KAUST.
The devices built and tested
Starting from silicon-doped β-Ga₂O₃ substrates, the team constructed two types of components. The first is a Fin Field-Effect Transistor (FinFET), a structure with fin channels ensuring greater stability and current control capability compared to conventional planar MOSFETs. The second is a logic inverter, also known as a NOT gate, a fundamental element of any digital circuit. Both devices demonstrated stable and reliable operation at a temperature of 2 Kelvin.
While not the first to operate at such low temperatures - there are cryogenic components based on other materials - those presented by KAUST represent the first demonstration of transistors and logic inverters made with an ultra-wide bandgap semiconductor in extreme cryogenic conditions. The distinction is significant: UWBG semiconductors combine the ability to withstand both high thermal stresses and cryogenic conditions in a single material, opening the possibility of creating monolithic cryogenic circuits - entirely built with a single material - which would significantly simplify the architecture of advanced electronic systems.
Applications and what comes next
The researchers identify two main application areas. In quantum computing, quantum processors typically operate at temperatures on the order of 4 Kelvin or lower, and the associated control and readout electronics must work close to the quantum chip. For space applications, the advantage of β-Ga₂O₃ lies in the thermal range it can tolerate: planetary probes and satellites are exposed to temperature variations that can range from a few Kelvin - in the deep shadow areas of space - to hundreds of degrees Celsius near the Sun or during re-entry phases.
The research group has outlined a roadmap that envisions the development of a broader family of components in β-Ga₂O₃, including radio frequency transistors, photodetectors, and memory cells. The stated goal is to scale the demonstrations of individual devices towards integrated and complex cryogenic chips, further pushing performance limits in the ultra-cold regime. This is a path that will require advances in both manufacturing and electrical characterization under cryogenic conditions.