Realizing Hyper-Functional Sensors and Transistors
Imagine non-volatile memories and ferroelectric field-effect transistors with logic states that require no power to maintain. Add to these, low-power transistors that can beat the subthreshold slope limit of conventional transistors. These tantalizing devices that exploit ferroelectric-semiconductor interfaces have been proposed, but their realization has been thwarted. Materials integration has been the problem. Replacing the ferroelectric with a multiferroic in such heterostructures would enable hypersensitive temperature, pressure, or magnetic field sensors relevant to the needs of the United States Air Force. The critical missing link to functional embodiments of these concepts is the ability to directly integrate high-performance ferroelectrics or multiferroics with high-performance semiconductors.
Darrell Schlom, Materials Science and Engineering, is meeting this long-standing challenge and enabling a new generation of hyper-functional oxide electronics. His secret is the employment of a recently discovered high-performance oxide semiconductor that is structurally and chemically compatible with ferroelectric and multiferroic oxides. This interface is crucial to the performance of the devices, since direct growth of ferroelectrics or multiferroics on mainstream semiconductors is accompanied by extensive interdiffusion or chemical reactions that degrade the properties of the oxide, the underlying semiconductor, or both. This degradation leads to incapacitating defects at the semiconductor-oxide interface.
With collaborators at Seoul National University and Leibniz Institute for Crystal Growth, Schlom is developing lattice-matched single crystal substrates for the growth of the high quality oxide semiconductor material: BaSnO3-based heterostructures. With these improved substrates, they will then grow and evaluate proof-of-concept BaSnO3-based oxide heterostructures for hyper-functional oxide electronics. These heterostructures exploit the exceptional functionalities of chemically and structurally compatible perovskite oxides to make smart-FETs, field-effect transistors, by integrating high-K, ferroelectric, multiferroic, and other functionalities with the high mobility BaSnO3 channel layer to make high-performance transistors and smart-FET sensors.