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 from Brightsurf:

Perspectives of infrared spectroscopy in quantitative estimation of proteins
The present review describes the basic principle and the instrumentation of IR spectroscopy along with its advancements.

A new method to measure optical absorption in semiconductor crystals
Tohoku University researchers have revealed more details about omnidirectional photoluminescence (ODPL) spectroscopy - a method for probing semiconducting crystals with light to detect defects and impurities.

Properties of catalysts studied with gamma ray resonance
Steam-assisted oil extraction methods for heavy deposits have long been the focus of attention at Kazan Federal University.

Researchers demonstrate record speed with advanced spectroscopy technique
Researchers have developed an advanced spectrometer that can acquire data with exceptionally high speed.

Spectroscopy approach poised to improve treatment for serious heart arrhythmia
Researchers have demonstrated that a new mapping approach based on near infrared spectroscopy can distinguish between fat and muscle tissue in the heart.

Late blight research pairs spectroscopy with classic plant pathology diagnostics
Gold and colleagues at the University of Wisconsin-Madison recently published research showing how they used contact spectroscopy to non-destructively sense how plant pathogens differentially damage, impair, and alter plant traits during the course of infection.

Doing more with terahertz: Simplifying near-infrared spectroscopy systems
Researchers from Beihang University, China, and Tokushima University, Japan, have developed a terahertz spectroscopy scheme that offers outstanding resolution using a single laser.

A new horizon for vibrational circular dichroism spectroscopy
(1) The development of solid state and time-step VCD methods opened a new horizon to reveal the mechanism of chirality amplification from microscopic to supramolecular scales.

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.

Read More: Spectroscopy News and Spectroscopy Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.