News: Suppliers
13 July 2021
Hamamatsu develops system for quantitatively evaluating GaN crystal quality
Japan’s Hamamatsu Photonics K.K. – which designs and manufactures devices that measure luminous efficiency based on the photoluminescence (PL) emitted from luminescent materials – has developed the C15993-01 gallium nitride (GaN) crystal evaluation system that leverages omnidirectional photoluminescence (ODPL) spectroscopy along with the firm’s unique light detection technologies including optical design and data processing.
ODPL spectroscopy is a novel technique for accurately evaluating the quality of compound semiconductor crystals such as GaN by quantifying structural defects and impurities within the crystal.
In traditional measurement methods utilizing PL, the quality of semiconductor crystals such as GaN is evaluated based on the intensity and wavelength-specific information of PL emitted in one direction from a sample crystal. PL measurement methods allow rapid non-contact and non-destructive evaluation of crystal quality. However, these methods have issues such as poor reproducibility and poor quantitative determination because measurement results depend on the detector position and angle and also on conditions for irradiating the crystal with light.
Against this backdrop, in 2016 Hamamatsu Photonics and a research group at Tohoku University’s Institute of Multidisciplinary Research for Advanced Materials headed by associate professor Kazunobu Kojima and professor Shigefusa Chichibu succeeded in making highly reproducible measurements of PL intensity emitted in all directions from a GaN crystal by using an integrating sphere. At the same time, this allowed the firm to discover that the internal quantum efficiency (IQE) of GaN crystals could be calculated from the measurement results by also using its unique calculation method. Then, using the IQE of the GaN crystals as an index, the firm established an ODPL spectroscopy measurement method for quantitatively evaluating the crystal quality.
The ODPL measurement system accurately evaluates GaN crystal quality. Hamamatsu has now applied its light detection and optical design technologies to create new software for this purpose. It not only accurately measures the PL intensity (over a wavelength range 300-950nm) emitted in all directions from GaN crystals via a 3.3-inch Spectralon integrating sphere but also automatically calculates IQE based on the measurement results. This in turn led to developing an ODPL measurement system that quantitatively evaluates GaN crystal quality using ODPL spectroscopy. The firm also optimized the placement of optical components to make the equipment components such as the integrating sphere, Czerny-Turner monochromator and optical systems more compact (725mm x 380mm x 417mm). A newly developed sliding sample holder (with a substrate size of 6mm x 6mm x 1mm to 17mm x 17mm x 1mm, and inner diameter of about 15mm) is also provided to make it easier to place the GaN crystal.
Since the ODPL measurement system can quantitatively evaluate GaN crystal quality using ODPL spectroscopy, it is expected to serve as a powerful tool that can greatly boost the efficiency of R&D on improving GaN crystal quality.
Hamamatsu aims to make ODPL spectroscopy measurements an industry standard for quantitative evaluation of GaN crystal quality. “We will also continue to design ever more versatile equipment that supports larger GaN crystal wafers to help streamline the quality inspection process on future mass production lines,” adds the firm.
Sales of the new ODPL measurement system begin on 2 August for researchers at universities and semiconductor substrate manufacturers both in Japan and overseas. The system is being presented at the ‘SEMI Partner Search - For Power & Compound’ online event on 14 July.
