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2014-02-04

Novel nanoscale contacts may facilitate downscaling of electronic devices

A new way to form nanoscale electrical contacts may be very important for the continuous development of smaller and faster electronics. This result is shown in a research report published in Nature Communications.

Researchers at Halmstad University, in collaboration with the Nanometer Structure Consortium at Lund University and Voronezh State Technical University in Russia, have demonstrated that nanoscale metal-semiconductor contacts realized by a bottom-up technique exhibit different electrical properties than contacts fabricated by conventional techniques. This discovery may be very important for further downscaling of electronic devices.

Electrical contacts between metals and semiconductors are fundamentally important for all manufacturing of electronics. Such contacts were in fact the first investigated semiconductor devices with seminal studies carried out already in the mid-1800s. Although these contacts are among the most widely studied electronic devices, there are still important unanswered questions related to their electrical properties and how these can be tailored. Further improvement of these contacts is considered one of the most serious challenges for further downscaling of electronics. In particular, the possibility to engineer the energy barrier (so-called Schottky barrier) that governs the current between the metal and semiconductor is highly desirable.

Gold particle and nanowire

In the newly published study, the electrical properties of the nanoscale contact formed between a gold particle and a semiconductor nanowire made of gallium arsenide was investigated in great detail. This has been made possible by highly advanced manufacturing and selective contacting of the particle and the nanowire. These nanoscale contacts differ significantly from conventional metal-semiconductor contacts not only due to substantially down-sized dimensions, but also because they are grown in an epitaxial bottom-up process at high temperatures where the gold particle catalyses the growth of the nanowire.

The most striking observation in the study is that the Schottky barrier between the gold particle and nanowire is strongly suppressed compared to any other comparable contacts reported so far in the literature.

– This observation is puzzling and we have done extensive studies to verify our results and to develop a physical model of the phenomenon”, says Professor Håkan Pettersson, who is the principle investigator for the research.

Key technology

The changed electrical properties can be understood in terms of a strongly modified contact surface between gold particle and nanowire. An electrically charged dipole layer is formed at the interface, in addition to a reduced density of surface states. These interesting properties, taken together with the small contact area, create a nanocontact with strongly reduced Schottky barrier.

– These findings may be of great importance and can potentially be used for tailoring the electric properties of nanocontacts by a smart design of the contact surface between metal and semiconductor. This could be developed into a key technology for further downscaling of electronics, says Håkan Pettersson.

Another very interesting application of these nanocontacts, as also demonstrated in the article, is that they can be used as extremely compact sensors that detect light.

Publication:

The article “Strong Schottky barrier reduction at Au-catalyst/GaAs-nanowire interfaces by electric dipole formation and Fermi-level unpinning” is published in Nature Communications. Read the article here.external link

Nanocontact with selective leads attached to gold particle (left) and to nanowire (right).

"These findings may be of great importance", says Professor Håkan Pettersson.

Updated 2014-02-18