Scientists design tougher flash memory device for space missions

The researchers have been able to build a flash memory device that can withstand the hazards encountered by space probes, including exposure to radiation and huge temperature swings, which can be challenging for traditional electronic circuits.

Although semiconductors are usually made from silicon, gallium oxide allows scientists to build devices that can support high currents and voltages with low energy losses.  In addition to space missions, the flash memory device could potentially be used in locations with risk of radiation or extreme conditions on Earth. 

Gallium oxide is an ultra-wide band gap semiconductor material. It is usually a poor conductor of electricity, but incorporating certain impurities can enable it to carry an electrical current.

“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,” said PhD candidate Vishal Khandelwal, a member of the research team. 

The KAUST team’s device is a transistor containing a floating gate layer, which captures electrons to store data.

Its design is similar to conventional flash memory devices, but instead of silicon, the device contains a layer of gallium oxide only 50 nanometers thick. On top is a tiny piece of titanium nitride, enclosed in a very thin layer of insulating material, which acts as the floating gate.  

To programme data into the device, the researchers apply a positive voltage pulse that sends electrons from the gallium oxide through the insulator and into the floating gate, where they are trapped. In contrast, a negative voltage can erase the data by sending the electrons back into the gallium oxide. 

Because of gallium oxide’s unusually wide band gap, there is a large difference between the device’s programmed and erased states. This property helps the device retain its data for more than 80 minutes.

At the moment, programming and erasing the device requires relatively long voltage pulses of about 100 milliseconds. However, the team is reportedly working on reducing these pulses.

“Further development in gallium oxide material quality and device design will give better memory properties for practical extreme-environment applications,” said team leaderXiaohang Li.

The researchers’ findings were published in the Japanese Journal of Applied Physics.