Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Breakthrough to the development of energy-saving devices for the next generation

21.10.2015

Towards the development of a new evaluation method of semiconductors by using terahertz (THz) waves

Wide-gap semiconductors such as gallium nitride (GaN) are widely used for optical devices such as blue LED and are also anticipated as materials for next-generation energy saving power devices and solar cells.


As shown in Figure a, in the neighborhood of the surface of semiconductor of GaN, the energy band is bent due to the surface potential. It is thought that photoexcited carriers are accelerated by the band bending, thereby radiating THz. It is also thought that the change in THz wave emission intensity due to defects, as shown in Figure b, is because the energy band bent significantly due to electrons trapped by defects near the surface, which further accelerated carriers. This shows that LTEM is effective for measuring the defect density of the surface of wide-gap semiconductors and their distribution of the surface potential.

Credit: Osaka University

However, the quality of GaN crystals does not come up to that of conventional semiconductor materials such as silicon (Si) and this prevents GaN from being used for power devices.

For that reason, the establishment of technology for producing high-quality crystals with fewer defects and rearrangement is expected, and the development of a new evaluation technology is crucial.

A group of researchers led by Iwao Kawayama, an associate professor of the Institute of Laser Engineering at Osaka University, in cooperation with Screen Holdings Co., Ltd., succeeded in visualizing changes in defect density on the surface of GaN through the laser terahertz emission microscope (LTEM) which measures THz waves generated by laser emission.

This group's discovery shows that LTEM is useful as a new method for evaluating the quality of wide-gap semiconductors and it is also expected that LTEM will bring a breakthrough in the development of next-generation optical devices, super high frequency devices, and energy devices.

The group examined the intensity distribution of THz generated by radiating ultraviolet femtosecond laser pulses on the surface of GaN crystal through LTEM.

As a result, it was found that there were regions with high intensity of THz emission and ones with low intensity of THz emission.

Additionally, when the LTEM image was compared with the image obtained through photoluminescence (PL) using a conventional method, it was found that there was a strong correlation between the distribution of emission intensity due to lattice defects and the intensity distribution of THz wave emission.

Furthermore, from results measurement through modification of excited lasers, it was confirmed that THz emission needs excitation light with larger energy than the band gap energy.

###

This research was featured in the electronic version of Scientific Reports (UK) on September 9, 2015.

Iwao Kawayama | EurekAlert!

More articles from Power and Electrical Engineering:

nachricht Researchers use light to remotely control curvature of plastics
23.03.2017 | North Carolina State University

nachricht TU Graz researchers show that enzyme function inhibits battery ageing
21.03.2017 | Technische Universität Graz

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Researchers create artificial materials atom-by-atom

28.03.2017 | Physics and Astronomy

Researchers show p300 protein may suppress leukemia in MDS patients

28.03.2017 | Health and Medicine

Asian dust providing key nutrients for California's giant sequoias

28.03.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>