Researchers indicate that growing electronic components directly onto a semiconductor eliminates the problem of electron scattering.
Faster computers require more device density on chip. As a result, the devices have to be smaller than ever. However, in smaller electronic devices, the electrons flow through has to be very close to the interface between the semiconductor and the metallic gate used to turn the transistor on and off. The surface oxidation and other surface contaminants cause unwanted scattering of electrons flowing through the channel, and also lead to instabilities and noise that are particularly problematic for quantum devices.
Researchers suggest that growing electronic components directly onto a semiconductor block avoids oxidation scattering that slows and impedes electronic operation.
“In the new work we create transistors in which an ultra-thin metal gate is grown as part of the semiconductor crystal, preventing problems associated with oxidation of the semiconductor surface,” says lead author Yonatan Ashlea Alava.
“We have demonstrated that this new design dramatically reduces unwanted effects from surface imperfections, and show that nanoscale quantum point contacts exhibit significantly lower noise than devices fabricated using conventional approaches,” says Yonatan, a FLEET Ph.D. student.
What is electron scattering?
Electron scattering is a limiting factor in integrated circuits and transistors. When electrons travel in solid, the electrostatic forces within matter interaction deflect the electron trajectory from the original path by the Lorentz force. This unwanted deflection is called electronic scattering.
Moreover, the surface of the semiconductors often has high levels of unwanted charge trapped by the unsatisfied chemical bonds. This causes electron scattering in the channel and reduces the device conductivity. Therefore, as the devices get smaller, and the conductive surface gets closer to the surface, the conductivity and the overall performance declines rapidly.
About the research
Researchers from UNSW, in collaboration with wafer growers at Cambridge University, indicated that this problem can be eliminated by growing an epitaxial aluminum gate before removing the wafer from the growth chamber.
The researchers characterized the devices using low-temperature transport measurements, and demonstrated that the epitaxial gate design can greatly reduce surface-charge scattering, with up to 2.5× increase in conductivity.
They also showed that the epitaxial aluminum gate can be patterned to make nanostructures.
“This new all single-crystal design will be ideal for making ultra-small electronic devices, quantum dots, and for qubit applications,” comments group leader Prof Alex Hamilton at UNSW.
The research appeared in the journal Applied Physics Letters.