This is a false-color, plan-view SEM image of a lateral gallium oxide field effect transistor with an optically defined gate. Source: Air Force Research Laboratory For decades, scientists and manufacturers have been looking for an alternative to silicon for use in microelectronics and semiconductor technology.

This is mostly because silicon has limitations in power applications. As a general rule, designers are looking for ways to reduce excess power consumption and heat generation. This is done through scaling devices, but the technologies used today are already scaled close to their limits for the operating voltage needed in many applications.

Not surprisingly, designers and researchers have turned to alternate materials to meet the needs in current and emerging applications. Transparent conductive oxides are emerging materials in semiconductor technology that offer a combination of conductivity and transparency over the visual spectrum.

Researchers at the Air Force Research Laboratory have been studying one conductive oxide in particular that allows it to function in power switching. Researchers believe this material, gallium oxide or Ga2O3, may be applicable for devices such as field effect transistors (FET). FETs could greatly benefit from gallium oxide’s large critical electric field strength, a quality that could enable the design of FETs with small geometries and aggressive doping profiles that would destroy any other FET material.

Ga2O3 is flexible for various applications because of its broad range of possible conductivities — from highly conductive to very insulating — and high breakdown-voltage capabilities due to its electric field strength. Gallium oxide can also be scaled down to an extreme degree with wafers that can be grown from the melt, lowering manufacturing costs.

"The next application for gallium oxide will be unipolar FETs for power supplies," says Gregg Jessen, principal electronics engineer at the Air Force Research Laboratory. "Critical field strength is the key metric here, and it results in superior energy density capabilities. The critical field strength of gallium oxide is more than 20 times that of silicon and more than twice that of silicon carbide and gallium nitride."

The researchers documented their findings in an American Institute of Physics paper where they present the possible manufacturing methods for Ga2O3 wafers, the ability to control electron density and other challenges. The findings indicate that unipolar Ga2O3 devices will dominate and offer details on how Ga2O3 applications will function in different types of FETs.