B01 group

B01-1 Multiscale characterization of singularity structures and behaviors thereof

    Principal Investigator / Akira Sakai (Osaka University / Professor)
  • Co-Investigator / Yasuhiko Imai (Japan Synchrotron Radiation Research Institute / Associate Senior Scientist)

In situ Nanobeam X-ray Diffraction (nanoXRD) with 100-nm-scale spatial resolution and sub-nano-second time resolution enables a wide-range analysis of local strain and domain textures in semiconductor crystals and devices. In addition, an effective combination of nanoXRD and microscopy methods detecting microstructures and distribution of defects realizes multiscale structural characterization from nanometer to millimeter. In this project, we focus on the singularity structures and behaviors thereof mainly in nitride semiconductor crystals, such as nano-voids, dislocations,
polar/non-polar lattices influencing piezoelectric effects, etc. Being supplied with several singularity-structure-controlled materials and devices from other groups, we perform three-dimensional precise structural analysis and in situ dynamic characterization for them. By exploiting active functions of the singularity structures, we systematize extended crystallography as a new field of study and contribute to the innovation of next generation green electronics.

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B01-2 Study of dynamics of carrier trapping/scattering in singularity crystal structure by means of positron annihilation

  • Principal Investigator / Akira Uedono (University of Tsukuba / Professor)
  • Co-Investigator / Nagayasu Oshima (National Institute of Advanced Industrial Science and Technology / Senior Researcher)
  • Co-Investigator / Masatomo Sumiya (National Institute for Materials Science / Chief Researcher)
  • Co-Investigator / Shoji Ishibashi (National Institute of Advanced Industrial Science and Technology / Leader, Team)
  • Co-Investigator / Hironori Okumura (University of Tsukuba / Assistant Professor)

Positron annihilation is a non-destructive detection tool for vacancy-type defects or open spaces in materials (Figure A). Using this technique, one can study such singularity structures with high sensitivity, and determine their species, concentrations and depth distributions. The purpose of the present research as follows; (i) a study of carrier trapping/scattering phenomena and their optical reactions, and (ii) developments of the measurement system in order to use a positron as a probe of electric field (Figure B and C). Measurement systems equipped with positron beam, illumination system, electron beam, and bias applying electronics are installed at University of Tsukuba and National Institute of Advanced Industrial Science and Technology. We use the positron annihilation spectroscopy to study properties of the singularity structures from a view of material science, and propose guidelines for the fabrication of electric devices using such structures.

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B01-3 3D spectroscopic characterization of crystal singularities and application of defects based on phonon science

  • Principal Investigator / Yoshihiro Isitani (Chiba University / Professor)
  • Co-Investigator / Yuzo Shinozuka (Wakayama University / Professor)
  • Co-Investigator / Bei Ma (Chiba University / Research Associate)

In this study, we characterize various crystal singularities and its application to the control of electronic and radiative properties of wide bandgap semiconductors by observing the interactions between carriers and phonons.
(1) Nondestructive spatially resolved characterization of crystal singularities and their physical properties
 Characterization of structural properties such as strain, electronic states, and lattice vibration states in crystals of devices epitaxially grown on patterned substrates.
 3D images of strain and interaction potential fields of carriers and lattice vibrations, particularly in the vicinity of dislocations and point defects

Here, we pursue the sensitive detection of fields of strain and crystal defects by the enhancement of electric field of electromagnetic waves using antenna structures, and also characterize carrier and exciton dynamics in the fields possessing crystal singularities by resonant Raman measurements using two-wavelength laser beams. Numerical analysis of the dynamics including phonon processes under nonthermal condition is also conducted. We build a bridge across the issues of defects and device properties on the basis of these studies.
(2) Application of the physics of defects to the control of optical and electrical properties for devices
We investigate the improvement of carrier transport properties, radiative efficiency, and current extraction from multi-quantum well structures by controlling the localization and delocalization of phonons using crystal singularities and the resultant increase and decrease in the interaction between phonons and carriers.


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