Nav: Home

Probing semiconductor crystals with a sphere of light

June 06, 2019

Tohoku University researchers have developed a technique using a hollow sphere to measure the electronic and optical properties of large semiconducting crystals. The approach, published in the journal Applied Physics Express, improves on current photoluminescence spectroscopy techniques and could lead to energy savings for mass producers, and thus consumers, of power devices.

Semiconducting crystals are used to make electronic devices like microprocessor chips and transistors. Manufacturers need to be able to detect crystal defects and test their energy conversion efficiency. One way to do this is to measure their 'internal quantum efficiency', or their ability to generate photons from electrons excited by an electric current or an excitation laser. Currently available methods limit the sample size that can be tested at a time.

Advanced materials scientist Kazunobu Kojima of Tohoku University and colleagues devised a modified approach to photoluminescence spectroscopy that can test larger samples.

Standard photoluminescence spectroscopy detects the relative amount of light emitted by a semiconductor crystal when an excitation laser is shone on it. Light energy is lost through these excitation and emission processes, so scientists have been experimenting with photoluminescence spectroscopy that uses an 'integrating sphere' to minimize the loss of photons, the elementary particles of light.

Integrating spheres collect both the excitation light and the light emitted from a sample lying inside it, where the light is diffusively reflected inside until it becomes uniformly dispersed. The uniform distribution of light improves the accuracy and repeatability of internal quantum efficiency testing. But this means that the size of the crystal being tested is ultimately limited by the size of the sphere.

Kojima and colleagues found they could still test the internal quantum efficiency of a crystal when it was placed directly outside the sphere, allowing larger samples to be used.

They conducted their tests on a semiconducting crystal called gallium nitride, which is commonly used in LEDs and is expected to be used in electronic devices because of its superior properties.

"This 'omnidirectional photoluminescence' spectroscopy can be used to evaluate the quality of large-sized crystals or semiconductor wafers, which are essential for the mass production of power devices," says Kojima, adding that this could lead to energy saving and reduce production costs.
-end-


Tohoku University

Related Spectroscopy Articles:

Unraveling the optical parameters: New method to optimize plasmon enhanced spectroscopy
Plasmon enhanced spectroscopies allow to reach single molecule sensitivity and a lateral resolution even down to sub-molecular resolution.
Nanoscale spectroscopy review showcases a bright future
A new review authored by international leaders in their field, and published in Nature, focuses on the luminescent nanoparticles at the heart of many advances and the opportunities and challenges for these technologies to reach their full potential.
Researchers combine advanced spectroscopy technique with video-rate imaging
For the first time, researchers have used an advanced analytical technique known as dual-comb spectroscopy to rapidly acquire extremely detailed hyperspectral images.
Quantum logic spectroscopy unlocks potential of highly charged ions
Scientists from the PTB and the Max Planck Institute for Nuclear Physics (MPIK), both Germany, have carried out pioneering optical measurements of highly charged ions with unprecedented precision.
Spectroscopy: A fine sense for molecules
Scientists at the Laboratory for Attosecond Physics have developed a unique laser technology for the analysis of the molecular composition of biological samples.
Fluorescence spectroscopy helps to evaluate meat quality
Scientists of Sechenov University jointly with their colleagues from Australia proposed a new, quicker and cheaper way to assess meat quality.
Single-particle spectroscopy of CsPbBr3 perovskite reveals the origin low electrolumine
Researchers from Tokyo Institute of Technology (Tokyo Tech) used the method of single-particle spectroscopy to study electroluminescence in light-emitting devices.
'Resonance' raman spectroscopy with 1-nm resolution
Tip-enhanced Raman spectroscopy resolved 'resonance' Raman scattering with 1-nm resolution in ultrathin zinc oxide films epitaxially grown on a single-crystal silver surface.
Improved functional near infrared spectroscopy enables enhanced brain imaging
In an article published in the peer-reviewed SPIE publication Neurophotonics, 'High density functional diffuse optical tomography based on frequency domain measurements improves image quality and spatial resolution,' researchers demonstrate critical improvements to functional Near Infrared Spectroscopy (fNIRS)-based optical imaging in the brain.
Raman spectroscopy poised to make thyroid cancer diagnosis less invasive
Researchers have demonstrated that an optical technique known as Raman spectroscopy can be used to differentiate between benign and cancerous thyroid cells.
More Spectroscopy News and Spectroscopy Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Teaching For Better Humans 2.0
More than test scores or good grades–what do kids need for the future? This hour, TED speakers explore how to help children grow into better humans, both during and after this time of crisis. Guests include educators Richard Culatta and Liz Kleinrock, psychologist Thomas Curran, and writer Jacqueline Woodson.
Now Playing: Science for the People

#556 The Power of Friendship
It's 2020 and times are tough. Maybe some of us are learning about social distancing the hard way. Maybe we just are all a little anxious. No matter what, we could probably use a friend. But what is a friend, exactly? And why do we need them so much? This week host Bethany Brookshire speaks with Lydia Denworth, author of the new book "Friendship: The Evolution, Biology, and Extraordinary Power of Life's Fundamental Bond". This episode is hosted by Bethany Brookshire, science writer from Science News.
Now Playing: Radiolab

Space
One of the most consistent questions we get at the show is from parents who want to know which episodes are kid-friendly and which aren't. So today, we're releasing a separate feed, Radiolab for Kids. To kick it off, we're rerunning an all-time favorite episode: Space. In the 60's, space exploration was an American obsession. This hour, we chart the path from romance to increasing cynicism. We begin with Ann Druyan, widow of Carl Sagan, with a story about the Voyager expedition, true love, and a golden record that travels through space. And astrophysicist Neil de Grasse Tyson explains the Coepernican Principle, and just how insignificant we are. Support Radiolab today at Radiolab.org/donate.