Exposure to radiation and extreme temperature swings are two of the many hazards that space probes face. Now, KAUST researchers have created the world's first flash memory device made of gallium oxide, which can withstand extreme temperatures far better than conventional electronics.
Gallium oxide-based devices can operate in extreme environments, such as outer space, where they can withstand high temperatures and radiation without serious degradation. Image Credit: ©2023 KAUST; Eliza Mkhitaryan.
Gallium oxide is a semiconductor; while it is normally a poor conductor of electricity, the addition of certain impurities allows it to carry an electrical current. It has numerous benefits over silicon, the semiconductor used in the majority of computer chips. Gallium oxide, for instance, can support high currents and voltages with low energy losses and is simple to grow into high-quality films using low-cost techniques.
Above all, it is challenging.
Gallium oxide-based devices have become a prominent choice to operate in adverse environments, especially in space exploration, because it can withstand high temperatures and radiation without serious degradation.
Vishal Khandelwal, PhD Candidate, King Abdullah University of Science and Technology
Transistors and diodes can also be built from gallium oxide. However, for gallium oxide electronics to thrive, researchers needed to demonstrate that the material could also be used in memory devices.
The device developed is a transistor with a floating gate layer that captures electrons to store data. This fundamental design is already in use in traditional flash memory devices. Instead of silicon, the new device has a thin layer of gallium oxide 50 nm thick. The floating gate is a minuscule fragment of titanium nitride enveloped in a very thin layer of insulating material above the gallium oxide.
The investigators use a positive voltage pulse to program data into the floating gate, which sends electrons from the gallium oxide through the insulator and into the floating gate, where they are trapped. A negative voltage can remove the data by reintroducing electrons into gallium oxide. The position of these electrons impacts how well the gallium oxide conducts electricity, which can be used to read the memory device’s state.
Gallium oxide has an uncommonly wide band gap—a measure of the energy required to free its electrons—which means that even at high operating temperatures, there is a significant difference between the device’s programmed and erased states. This property contributes to the memory’s stability, and the prototype device could retain data for more than 80 minutes.
For now, programming and erasing the device necessitate relatively long voltage pulses of around 100 milliseconds, which the team hopes to reduce.
Further development in gallium oxide material quality and device design will give better memory properties for practical extreme-environment applications.
Xiaohang Li, King Abdullah University of Science and Technology
Xiaohang Li guides the team.
Journal Reference:
Khandelwal, V., et al. (2023). Demonstration of β-Ga2O3 nonvolatile flash memory for oxide electronics. Japanese Journal of Applied Physics. doi.org/10.35848/1347-4065/acdbf3.