Semiconductors and the Quantum World

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"Map" of electrons: This graph, obtained by the SX-ARPES method, shows bright bands representing states occupied by electrons in the energy/momentum space. The band in semiconductor gallium nitride (GaN) is clearly separated from the superconducting states (surrounded by light blue lines) in niobium nitride (NbN). This means that the determining electrons in the two materials do not interact with each other. Permission: Paul Scherrer Institute/Tianlun Yu

Quantum effects in superconductors could represent a new and unexpected change in semiconductor technology. Researchers at New York's Paul Scherrer Institute PSI and Cornell University have identified a composite material that could integrate quantum devices into semiconductor technology and make electronic components significantly stronger. They publish their findings in the journal Science Advances. The publication date is December 23, 2021. We can say that there is no harm in expressing this. “Semiconductors and the Quantum World” will now be much closer than before.

Our current electronic infrastructure is mainly based on semiconductors. This class of material emerged in the middle of the 20th century and has evolved and changed since then.

Differences Between Conductor Semiconductor and Insulators
What are the differences between semiconductors, conductors and insulators? Ref: electricaltechnology

Currently, there are the most important challenges in semiconductor electronics. We can list them as follows.

  • bandwidth of data transmission.
  • Energy efficiency
  • Additional improvements to increase information security

It is thought that making use of quantum effects for the substances mentioned above will most likely be a breakthrough.

The quantum effects that can occur in superconducting materials are particularly noteworthy. Superconductors are materials whose electrical resistance disappears when cooled below a certain temperature. The fact that quantum effects in superconductors can be exploited has already been demonstrated in the first quantum computers.

To find possible successors to today's semiconductor electronics, some researchers, including a group at Cornell University, are investigating so-called heterojunctions, or structures made of two different materials. More specifically, they are looking at layered systems of superconducting and semiconductor materials.

“It's been known for some time that you need to choose materials with very similar crystal structures for this so that there isn't any tension in the crystal lattice at the contact surface,” explains John Wright, who produced the heterojunctions for the new study.

Two suitable materials in this regard are the superconducting niobium nitride (NbN) and the semiconductor gallium nitride (GaN).

The latter already plays an important role in semiconductor electronics and is therefore well researched.

But until now, it was unclear exactly how electrons behave at the contact interface of these two materials, and whether it is possible for electrons from the semiconductor to interfere with superconductivity, thereby eliminating quantum effects.

As a result of the collaboration and experiments of researchers at the Paul Scherrer Institute PSI and Cornell University, they finally found that the electrons in both materials "hold themselves". No undesirable interactions were taking place that could potentially disrupt quantum effects.

Synchrotron Light Reveals Electronic Structures

PSI researchers used a well-established method in SLS's ADDRESS beamline.

The ADDRESS beamline is a high performance soft X-ray ripple beamline operating in the energy range of 300 eV to 1,6 keV.

The Swiss Light Source (SLS) at the Paul Scherrer Institute is a third generation synchrotron light source. With 2.4 GeV energy, it provides high-brightness photon beams for materials science, biology and chemistry research and enables research to be carried out.

What is Synchrotron Light?

Synchrotron radiation is electromagnetic radiation emitted when relatively charged particles are subjected to an acceleration (a ⊥ v) perpendicular to their velocity. It is produced artificially in some types of particle accelerators or naturally by fast electrons moving in magnetic fields. The radiation thus produced has a characteristic polarization and the frequencies produced can vary over a large part of the electromagnetic spectrum.

"With this method, we can visualize the bulk movement of electrons in the material," explains Tianlun Yu, who made measurements on the NbN/GaN heterostructure.

As a result of important research results, we can briefly say the following.

At the material boundary between niobium nitride NbN and gallium nitride GaN, the respective “bands” are clearly separated from each other. This tells the researchers that the electrons remain in their original material and do not interact with electrons in the neighboring material.

“The most important implication for us is that the superconductivity in niobium nitride remains intact even if this is placed atom by atom in such a way that it pairs with a gallium nitride layer,” Strocov says.

"With this, we were able to provide another piece of the puzzle that confirms: This layer system can lend itself to a new form of semiconductor electronics that embeds and exploits the quantum effects that occur in superconductors."

Source: techxplore

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